Multi-layer thermoplastic films and bags with enhanced light transmittance and methods for making the same

ABSTRACT

Implementations described herein include films with maintained or decreased light transmittance despite a reduction in gauge. In particular, one or more implementations include a multi-layer film with each layer having differing opacity agents. The combination of the two different opacity agents in two different layers can have a synergistic effect that provide decreased light transmittance. Indeed, in one or more embodiments a multi-layer film with differing opacity agents in each layer has a decreased light transmittance despite a reduction in gauge and opacity agents.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 16/204,111, filed Nov. 29, 2018 and entitled MULTI-LAYERTHERMOPLASTIC FILMS AND BAGS WITH ENHANCED LIGHT TRANSMITTANCE ANDMETHODS FOR MAKING THE SAME, which is a divisional of U.S. patentapplication Ser. No. 14/508,850 filed Oct. 7, 2014 and entitledMULTI-LAYER THERMOPLASTIC FILMS AND BAGS WITH ENHANCED LIGHTTRANSMITTANCE AND METHODS FOR MAKING THE SAME and issued on Feb. 5, 2019at U.S. Pat. No. 10,196,177, which is a continuation-in-part of U.S.patent application Ser. No. 13/299,177, filed Nov. 17, 2011 and entitledMULTI-LAYERED LIGHTLY-LAMINATED FILMS AND METHODS OF MAKING THE SAME andissued on Nov. 17, 2015 as U.S. Pat. No. 9,186,862, which is acontinuation-in-part of U.S. patent application Ser. No. 12/947,025,filed Nov. 16, 2010 and entitled DISCONTINUOUSLY LAMINATED FILM andissued on Dec. 10, 2013 as U.S. Pat. No. 8,603,609, which claims thebenefit of and priority to U.S. Provisional Application No. 61/261,673,filed Nov. 16, 2009. U.S. patent application Ser. No. 14/508,850 is alsoa continuation-in-part of U.S. patent application Ser. No. 13/289,829,filed Nov. 4, 2011 and entitled INCREMENTALLY-STRETCHED THERMOPLASTICFILMS AND BAGS WITH INCREASED HAZE and issued on Aug. 18, 2015 as U.S.Pat. No. 9,108,390. Each of the above-referenced patent and applicationsis hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION 1. The Field of the Invention

The present invention relates generally to thermoplastic films.Specifically, the invention relates multi-layer thermoplastic films withmaintained or decreased light transmittance despite a reduction in gaugeand/or opacity agents.

2. Background and Relevant Art

Thermoplastic films are a common component in various commercial andconsumer products. For example, grocery bags, trash bags, sacks, andpackaging materials are products that are commonly made fromthermoplastic films. Additionally, feminine hygiene products, babydiapers, adult incontinence products, and many other products includethermoplastic films to one extent or another.

The cost to produce products including thermoplastic film is directlyrelated to the cost of the thermoplastic film. Recently the cost ofthermoplastic materials has risen. In response, many attempt to controlmanufacturing costs by decreasing the amount of thermoplastic materialin a given product.

One way manufacturers may attempt to reduce production costs is tostretch the thermoplastic film, thereby increasing its surface area andreducing the amount of thermoplastic film needed to produce a product ofa given size. Common directions of stretching include “machinedirection” and “transverse direction” stretching. As used herein, theterm “machine direction” or “MD” refers to the direction along thelength of the film, or in other words, the direction of the film as thefilm is formed during extrusion and/or coating. As used herein, the term“transverse direction” or “TD” refers to the direction across the filmor perpendicular to the machine direction.

Common ways of stretching film in the machine direction include machinedirection orientation (“MDO”) and incremental stretching. MDO involvesstretching the film between pairs of smooth rollers. Commonly, MDOinvolves running a film through the nips of sequential pairs of smoothrollers. The first pair of rollers rotates at a speed less than that ofthe second pair of rollers. The difference in speed of rotation of thepairs of rollers can cause the film between the pairs of rollers tostretch. The ratio of the roller speeds will roughly determine theamount that the film is stretched. For example, if the first pair ofrollers is rotating at 100 feet per minute (“fpm”) and the second pairof rollers is rotating at 500 fpm, the rollers will stretch the film toroughly five times its original length. MDO stretches the filmcontinuously in the machine direction and is often used to create anoriented film.

To MDO a film, manufacturers commonly heat the film to an elevatedtemperature and stretch the film in the machine direction. Commonly,manufacturers will stretch the thermoplastic film between approximately300 to 500 percent of the film's original length or more.

Incremental stretching of thermoplastic film, on the other hand,typically involves running the film between grooved or toothed rollers.The grooves or teeth on the rollers intermesh and stretch the film asthe film passes between the rollers. Incremental stretching can stretcha film in many small increments that are evenly spaced across the film.The depth at which the intermeshing teeth engage can control the degreeof stretching. Often, incremental stretching of films is referred to asring rolling.

Stretched films of reduced thickness can allow manufacturers to use lessthermoplastic material to form a product of a given surface area orsize. Reducing the gauge (i.e., thickness) of a film; however, can makethe film more transparent or translucent. Consumers commonly associatethinner films and/or transparent films with weakness; and thus, may bedissuaded to purchase stretched films. Manufacturers may add pigmentsand/or additives, such as Ti02 or voiding agents, to add either colorand/or opacity to thinner films. Unfortunately, additives, such as Ti02and voiding agents can be expensive and/or often negatively impact thefilm strength properties, especially as the additive concentration isincreased. Furthermore, even pigmented films commonly become less opaqueupon stretching.

Optical measurements affecting opacity include light transmission, haze,and clarity. Light transmission is a measure of how much light isabsorbed when passing through a film. Haze measures wide angle lightscattering, and is a way of quantifying how well one can see contrastthrough films. Clarity measures narrow angle light scattering, and is away of quantifying the ability to resolve detail through a film. ASTMD1003-11 or the Standard Test Method for Haze and Luminous Transmittanceof Transparent Plastics describes how haze and other optical propertiesof films can be measured. ASTM D1003-11 is hereby incorporated byreference in its entirety.

The increasing transparency or decreasing the opacity of a film uponstretching may dissuade manufacturers to stretch a film or use thinnerfilms despite the potential material savings. For example, one commonuse of thermoplastic films is bags for liners in trash or refusereceptacles. Many consumers may prefer opaque and non-transparent trashbags that prevent others (i.e., neighbors) from viewing the contents inthe trash bag.

Accordingly, there are a number of considerations to be made inthermoplastic films and manufacturing methods.

BRIEF SUMMARY

One or more implementations of the present invention solve one or moreof the foregoing or other problems in the art with apparatus and methodsfor decreasing the light transmission of films. In particular, one ormore implementations of the present invention include multi-layer filmsthat have less light transmittance. Additionally, one or moreimplementations of the present invention include methods ofincrementally stretching multi-layer films to reduce their gauge byweight, while simultaneously decreasing the films' light transmittance.

Additional features and advantages of exemplary embodiments of thepresent invention will be set forth in the description which follows,and in part will be obvious from the description, or may be learned bythe practice of such exemplary embodiments. The features and advantagesof such embodiments may be realized and obtained by means of theinstruments and combinations particularly pointed out in the appendedclaims. These and other features will become more fully apparent fromthe following description and appended claims, or may be learned by thepractice of such exemplary embodiments as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. It should be noted that thefigures are not drawn to scale, and that elements of similar structureor function are generally represented by like reference numerals forillustrative purposes throughout the figures. Understanding that thesedrawings depict only typical embodiments of the invention and are nottherefore to be considered to be limiting of its scope, the inventionwill be described and explained with additional specificity and detailthrough the use of the accompanying drawings in which:

FIGS. 1A-1C illustrate views of various films structures in accordancewith one or more implementations of the present invention;

FIG. 2 illustrates a multi-layer thermoplastic film with decreased lighttransmittance in accordance with one or more implementations of thepresent invention;

FIG. 3A illustrates a schematic diagram of two thermoplastic films beinglightly laminated by MD intermeshing rollers in accordance with one ormore implementations of the present invention;

FIG. 3B illustrates an enlarged view of the two thermoplastic filmspassing together through the intermeshing rollers of FIG. 3A taken alongthe circle 3B of FIG. 3A to form a multi-layered lightly-laminatedthermoplastic film in accordance with one or more implementations of thepresent invention;

FIG. 4 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by passing thermoplastic film through theintermeshing rollers of FIG. 3A;

FIG. 5A a schematic diagram of two thermoplastic films being lightlylaminated by TD intermeshing rollers in accordance with one or moreimplementations of the present invention;

FIG. 5C illustrates an enlarged view of the two thermoplastic filmspassing together through the intermeshing rollers of FIG. 5A taken alongthe circle 5C of FIG. 5A to form a multi-layered lightly-laminatedthermoplastic film, FIG. 5B illustrates the film prior to passingthrough the intermeshing rollers and FIG. 5D illustrates the film afterpassing through the intermeshing rollers in accordance with one or moreimplementations of the present invention;

FIG. 6 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by passing thermoplastic film through theintermeshing rollers of FIG. 5A;

FIG. 7 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by passing thermoplastic film through theintermeshing rollers of both FIG. 3A and FIG. 5A;

FIG. 8 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by passing thermoplastic film throughdiagonal direction intermeshing rollers in accordance with one or moreimplementations of the present invention;

FIG. 9 illustrates a schematic diagram of a set of intermeshing rollersused to form a structural elastic like film (SELF) by impartingstrainable networks into the film while lightly laminating adjacentlayers of a film in accordance with one or more implementations of thepresent invention;

FIG. 10 illustrates a view of a multi-layered lightly-laminatedthermoplastic film created by passing thermoplastic film through theintermeshing rollers of FIG. 9;

FIG. 11 illustrates a view of another multi-layered lightly-laminatedthermoplastic film including strainable networks in accordance with oneor more implementations of the present invention;

FIG. 12 illustrates a bag incorporating the multi-layeredlightly-laminated film of FIG. 6 in accordance with one or moreimplementations of the present invention;

FIG. 13 illustrates a bag incorporating a multi-layeredlightly-laminated film in accordance with one or more implementations ofthe present invention;

FIG. 14 illustrates a bag incorporating a middle section having lightlybonded regions in accordance with one or more implementations of thepresent invention;

FIG. 15 illustrates a bag incorporating sections of different patternsof lightly bonded regions in accordance with one or more implementationsof the present invention;

FIG. 16 illustrates another bag incorporating sections of differentpatterns of lightly bonded regions in accordance with one or moreimplementations of the present invention;

FIG. 17 illustrates another bag incorporating a multi-layeredlightly-laminated film formed by passing thermoplastic film through MDring rolls in accordance with one or more implementations of the presentinvention;

FIG. 18 illustrates a bag incorporating a multi-layeredlightly-laminated film formed by passing thermoplastic film through MDring rollers and SELFing rollers in accordance with one or moreimplementations of the present invention;

FIG. 19 illustrates another bag incorporating a multi-layeredlightly-laminated film formed by passing thermoplastic film through MDring rollers, TD ring rollers, and SELFing rollers in accordance withone or more implementations of the present invention;

FIG. 20 illustrates another bag incorporating a multi-layeredlightly-laminated film formed by passing thermoplastic film through MDring rolls and SELFing rollers in accordance with one or moreimplementations of the present invention;

FIG. 21 illustrates a schematic diagram of a bag manufacturing processin accordance with one or more implementations of the present invention;

FIG. 22 illustrates a schematic diagram of another bag manufacturingprocess in accordance with one or more implementations of the presentinvention;

FIG. 23 illustrates a schematic diagram of yet another bag manufacturingprocess in accordance with one or more implementations of the presentinvention; and

FIG. 24 illustrates a schematic diagram of still another bagmanufacturing process in accordance with one or more implementations ofthe present invention.

DETAILED DESCRIPTION

One or more implementations of the present invention include apparatusand methods for decreasing the light transmission of films. Inparticular, one or more implementations of the present invention includemulti-layer films that have less light transmittance. Additionally, oneor more implementations of the present invention include methods ofincrementally stretching multi-layer films to reduce their gauge byweight, while simultaneously maintaining or decreasing the films' lighttransmittance.

In particular, one or more implementations include a multi-layer filmwith each layer having differing opacity agents. The combination of thetwo different opacity agents in two different layers can have asynergistic effect that provides for decreased light transmittance.Indeed, in one or more embodiments a multi-layer film with differingopacity agents in each layer has a decreased light transmittance despitea reduction in gauge.

For example, one or more implementations include a multi-layerthermoplastic film with one layer of the multi-layer film having a lightreflecting opacity agent and another layer having a light absorptionopacity agent. The combination of the two different opacity agents inthe two different layers of the multi-layer film can decrease lighttransmittance despite a reduction in a total amount of opacity agentsused in the film. Thus, one or more embodiments can appear to be moreopaque despite using less opacity agents, such as pigments, therebyresulting in significant cost savings.

As mentioned, one or more implementations of the present invention canprovide thermoplastic films, and products made there from, with reducedgauge yet decreased light transmittance. In other words, one or moreimplementations can provide thinner films without making the film moretransparent or translucent. Thus, one or more implementations can reducethe material needed to produce a product without compromising importantmaterial properties, such as opacity. One will appreciate in view of thedisclosure herein that such material reductions can provide significantcost savings by reducing an amount of raw material in a given product.

Additionally, consumers may associate thinner films with decreasedstrength. Indeed, such consumers may feel that they are receiving lessvalue for their money when purchasing thermoplastic film products withthinner gauges. One will appreciate in view of the disclosure hereinthat a consumer may not readily detect that one or more multi-layerfilms of the present invention has a reduced gauge. In particular, bydecreasing the light transmittance and stretching, the consumer mayperceive the film as being thicker and/or having increased strength.

As explained in greater detail below, one or more implementations of thepresent invention allow for decreased light transmittance, with less useof additives, such as pigments or voiding agents, to color or addopacity to a film. The reduction in additives can lead to significantcost savings. Additionally, the use of no, or less, additives such asvoiding agents can reduce or eliminate strength degradation associatedwith many additives.

In particular, one or more embodiments include films that are thinner,include less opacity agents, and have lower light transmissions thanstandard films. For example, one or more implementations include filmsthat are 20% thinner, include between 40 percent and 60 percent lessopacity agents, and have maintained or lower light transmission whencompared to standard quality while films used in the trash bag industry.

In addition to the foregoing, one or more implementations of the presentinvention include multi-layer films that are discontinuously bondedtogether. In other words, in one or more implementations the adjacentlayers of the multi-layer film can be incrementally separated. Theseparation between the layers can help diffuse light travelling throughthe multi-layer film.

In addition to helping to decrease light transmittance, thediscontinuous bonding can also enhance the strength and other propertiesof the film. In particular, one or more implementations provide forforming bonds between adjacent layers of a multi-layer film that arerelatively light such that forces acting on the multi-layer film arefirst absorbed by breaking the bonds rather than or prior to tearing orotherwise causing the failure of the layers of the multi-layer film.Such implementations can provide an overall thinner film employing areduced amount of raw material that nonetheless has maintained orincreased strength parameters. Alternatively, such implementations canuse a given amount of raw material and provide a film with increasedstrength parameters.

In particular, the weak bonds or bond regions of adjacent layers ofmulti-layer films in accordance with one or more implementations can actto first absorb forces via breaking of the bonds prior to allowing thatsame force to cause failure of the individual layers of the multi-layerfilm. Such action can provide increased strength to the multi-layerfilm. In one or more implementations, the weak bonds or bond regionsinclude a bond strength that is advantageously less than a weakest tearresistance of each of the individual films so as to cause the bonds tofail prior to failing of the film layers. Indeed, one or moreimplementations include bonds that the release just prior to anylocalized tearing of the layers of the multi-layer film.

Thus, in one or more implementations, the weak bonds or bond regions ofa multi-layer film can fail before either of the individual layersundergoes molecular-level deformation. For example, an applied straincan pull the weak bonds or bond regions apart prior to anymolecular-level deformation (stretching, tearing, puncturing, etc.) ofthe individual film layers. In other words, the weak bonds or bondregions can provide less resistive force to an applied strain thanmolecular-level deformation of any of the layers of the multi-layerfilm. The inventors have surprisingly found that such a configuration ofweak bonding can provide increased strength properties to themulti-layer film as compared to a monolayer film of equal thickness or amulti-layer film in which the plurality of layers are tightly bondedtogether (e.g., coextruded).

One or more implementations of the present invention provide fortailoring the bonds or bond regions between layers of a multi-layer filmto ensure weak bonding and associated increased strength. For example,one or more implementations include modifying or tailoring one or moreof a bond strength, bond density, bond pattern, or bond size betweenadjacent layers of a multi-layer film to deliver a film with strengthcharacteristics better than or equal to the sum of the strengthcharacteristics of the individual layers. Such bond tailoring can allowfor multi-layer films at a lower basis weight (amount of raw material)to perform the same as or better than higher basis weight monolayer orco-extruded films.

Relatively weak bonding and stretching of the two or more layers of themulti-layer film can be accomplished simultaneously through one or moresuitable techniques. For example, bonding and stretching may be achievedby pressure (for example MD ring rolling, TD ring rolling, DD ringrolling, stainable network lamination, or embossing), or with acombination of heat and pressure. Alternately, a manufacturer can firststretch the films and then bond the films using one or more bondingtechniques. For example, one or more implementations can includeultrasonic bonding to lightly laminate the film layers. Alternately oradditionally, adhesives can laminate the films. Treatment with a Coronadischarge can enhance any of the above methods. Prior to lamination, theseparate layers can be flat film or can be subject to separateprocesses, such as stretching, slitting, coating and printing, andcorona treatment.

As used herein, the terms “lamination,” “laminate,” and “laminatedfilm,” refer to the process and resulting product made by bondingtogether two or more layers of film or other material. The term“bonding”, when used in reference to bonding of multiple layers of amulti-layer film, may be used interchangeably with “lamination” of thelayers. According to methods of the present invention, adjacent layersof a multi-layer film are laminated or bonded to one another. Thebonding purposely results in a relatively weak bond between the layersthat has a bond strength that is less than the strength of the weakestlayer of the film. This allows the lamination bonds to fail before thefilm layer, and thus the film, fails.

The term laminate is also inclusive of coextruded multilayer filmscomprising one or more tie layers. As a verb, “laminate” means to affixor adhere (by means of, for example, adhesive bonding, pressure bonding,ultrasonic bonding, corona lamination, and the like) two or moreseparately made film articles to one another so as to form a multi-layerstructure. As a noun, “laminate” means a product produced by theaffixing or adhering just described.

In one or more implementations, the light lamination or bonding betweenlayers of a multi-layer film may be non-continuous (i.e., discontinuousor partial discontinuous). As used herein the terms “discontinuousbonding” or “discontinuous lamination” refers to lamination of two ormore layers where the lamination is not continuous in the machinedirection and not continuous in the transverse direction. Moreparticularly, discontinuous lamination refers to lamination of two ormore layers with repeating bonded patterns broken up by repeatingun-bonded areas in both the machine direction and the transversedirection of the film.

As used herein the terms “partially discontinuous bonding” or “partiallydiscontinuous lamination” refers to lamination of two or more layerswhere the lamination is substantially continuous in the machinedirection or in the transverse direction, but not continuous in theother of the machine direction or the transverse direction. Alternately,partially discontinuous lamination refers to lamination of two or morelayers where the lamination is substantially continuous in the width ofthe article but not continuous in the height of the article, orsubstantially continuous in the height of the article but not continuousin the width of the article. More particularly, partially discontinuouslamination refers to lamination of two or more layers with repeatingbonded patterns broken up by repeating unbounded areas in either themachine direction or the transverse direction.

Film Materials

As an initial matter, the thermoplastic material of the films of one ormore implementations can include, but are not limited to, thermoplasticpolyolefins, including polyethylene and copolymers thereof andpolypropylene and copolymers thereof. The olefin-based polymers caninclude the most common ethylene or propylene based polymers such aspolyethylene, polypropylene, and copolymers such as ethylenevinylacetate (EVA), ethylene methyl acrylate (EMA) and ethylene acrylicacid (EAA), or blends of such polyolefins.

Other examples of polymers suitable for use as films in accordance withthe present invention include elastomeric polymers. Suitable elastomericpolymers may also be biodegradable or environmentally degradable.Suitable elastomeric polymers for the film includepoly(ethylene-butene), poly(ethylene-hexene), poly(ethylene-octene),poly(ethylene-propylene), poly(styrene-butadiene-styrene),poly(styrene-isoprene-styrene), poly(styrene-ethylene-butylene-styrene),poly(ester-ether), poly(ether-amide), poly(ethylene-vinylacetate),poly(ethylene-methylacrylate), poly(ethylene-acrylic acid),poly(ethylene butylacrylate), polyurethane,poly(ethylene-propylene-diene), ethylene-propylene rubber.

The examples and description herein below refer to films formed fromlinear low-density polyethylene. The term “linear low densitypolyethylene” (LLDPE) as used herein is defined to mean a copolymer ofethylene and a minor amount of an olefin containing 4 to 10 carbonatoms, having a density of from about 0.910 to about 0.926, and a meltindex (MI) of from about 0.5 to about 10. For example, some examplesherein use an octene comonomer, solution phase LLDPE (MI=1.1; ρ=0.920).Additionally, other examples use a gas phase LLDPE, which is a hexenegas phase LLDPE formulated with slip/AB (MI=1.0; ρ=0.920). Still furtherexamples use a gas phase LLDPE, which is a hexene gas phase LLDPEformulated with slip/AB (MI=1.0; ρ=0.926). One will appreciate that thepresent invention is not limited to LLDPE, and can include “high densitypolyethylene” (HDPE), “low density polyethylene” (LDPE), and “very lowdensity polyethylene” (VLDPE). Indeed films made from any of thepreviously mentioned thermoplastic materials or combinations thereof canbe suitable for use with the present invention.

Indeed, one or more implementations of the present invention can includeany flexible or pliable thermoplastic material that may be formed ordrawn into a web or film. Furthermore, the thermoplastic materials mayinclude a single layer or multiple layers. The thermoplastic materialmay be opaque, transparent, translucent, or tinted. Furthermore, thethermoplastic material may be gas permeable or impermeable.

As used herein, the term “flexible” refers to materials that are capableof being flexed or bent, especially repeatedly, such that they arepliant and yieldable in response to externally applied forces.Accordingly, “flexible” is substantially opposite in meaning to theterms inflexible, rigid, or unyielding. Materials and structures thatare flexible, therefore, may be altered in shape and structure toaccommodate external forces and to conform to the shape of objectsbrought into contact with them without losing their integrity. Inaccordance with further prior art materials, web materials are providedwhich exhibit an “elastic-like” behavior in the direction of appliedstrain without the use of added traditional elastic. As used herein, theterm “elastic-like” describes the behavior of web materials which whensubjected to an applied strain, the web materials extend in thedirection of applied strain, and when the applied strain is released theweb materials return, to a degree, to their pre-strained condition.

In addition to a thermoplastic material, films of one or moreimplementations of the present invention can also include one or moreadditives. In particular, one or more embodiments include opacityagents. As used herein the term “opacity agent” refers to an agent thatwhen added to a thermoplastic film increases the opacity of the film(i.e., decreases the transparency or light transmittance through thefilm). One example of an opacity agent is pigments. Pigments can belight reflecting (e.g., white pigments) or light absorbing (e.g., blackpigments). Examples of pigments suitable for one or more implementationsinclude titanium dioxide, Antimony Oxide, Zinc Oxide, metal carbonates,White Lead, Lithopone, Clay, Magnesium Silicate, Barytes (BaSO4), andCalcium Carbonate (CaCO3).

Additional additives that may be included in one or more embodimentsinclude slip agents, anti-block agents, voiding agents, or tackifiers.Additionally, one or more implementations of the present inventioninclude films that are devoid of voiding agents. Some examples ofinorganic voiding agents include calcium carbonate, magnesium carbonate,barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate,calcium oxide, magnesium oxide, titanium oxide, zinc oxide, aluminumhydroxide, magnesium hydroxide, talc, clay, silica, alumina, mica, glasspowder, starch, etc. Organic voiding agents, polymers that areimmiscible in the major polymer matrix, can also be used. For instance,polystyrene is a can be used as a voiding agent in polyethylene andpolypropylene films.

One will appreciate in view of the disclosure herein that manufacturersmay form the films or webs to be used with the present invention using awide variety of techniques. For example, a manufacturer can formprecursor mix of the thermoplastic material and one or more additives.The manufacturer can then form the film(s) from the precursor mix usingconventional flat or cast extrusion or coextrusion to produce monolayer,bilayer, or multilayer films. Alternatively, a manufacturer can form thefilms using suitable processes, such as, a blown film process to producemonolayer, bilayer, or multilayer films. If desired for a given end use,the manufacturer can orient the films by trapped bubble, tenterframe, orother suitable process. Additionally, the manufacturer can optionallyanneal the films thereafter.

An optional part of the film-making process is a procedure known as“orientation.” The orientation of a polymer is a reference to itsmolecular organization, i.e., the orientation of molecules relative toeach other. Similarly, the process of orientation is the process bywhich directionality (orientation) is imposed upon the polymericarrangements in the film. The process of orientation is employed toimpart desirable properties to films, including making cast filmstougher (higher tensile properties). Depending on whether the film ismade by casting as a flat film or by blowing as a tubular film, theorientation process can require different procedures. This is related tothe different physical characteristics possessed by films made by thetwo conventional film-making processes; casting and blowing. Generally,blown films tend to have greater stiffness and toughness. By contrast,cast films usually have the advantages of greater film clarity anduniformity of thickness and flatness, generally permitting use of awider range of polymers and producing a higher quality film.

When a film has been stretched in a single direction (monoaxialorientation), the resulting film can exhibit strength and stiffnessalong the direction of stretch, but can be weak in the other direction,i.e., across the stretch, often splitting when flexed or pulled. Toovercome this limitation, two-way or biaxial orientation can be employedto more evenly distribute the strength qualities of the film in twodirections. Most biaxial orientation processes use apparatus thatstretches the film sequentially, first in one direction and then in theother.

In one or more implementations, the films of the present invention areblown film, or cast film. Blown film and cast film is formed byextrusion. The extruder used can be a conventional one using a die,which will provide the desired gauge. Some useful extruders aredescribed in U.S. Pat. Nos. 4,814,135; 4,857,600; 5,076,988; 5,153,382;each of which are incorporated herein by reference in their entirety.Examples of various extruders, which can be used in producing the filmsto be used with the present invention, can be a single screw typemodified with a blown film die, an air ring, and continuous take offequipment.

In one or more implementations, a manufacturer can use multipleextruders to supply different melt streams, which a feed block can orderinto different channels of a multi-channel die. The multiple extruderscan allow a manufacturer to form a multi-layered film with layers havingdifferent compositions. Such multi-layer film may later benon-continuously laminated with another layer of film to provide thebenefits of the present invention.

In a blown film process, the die can be an upright cylinder with acircular opening. Rollers can pull molten plastic upward away from thedie. An air-ring can cool the film as the film travels upwards. An airoutlet can force compressed air into the center of the extruded circularprofile, creating a bubble. The air can expand the extruded circularcross section by a multiple of the die diameter. This ratio is calledthe “blow-up ratio.” When using a blown film process, the manufacturercan collapse the film to double the plies of the film. Alternatively,the manufacturer can cut and fold the film, or cut and leave the filmunfolded.

In any event, in one or more embodiments, the extrusion process canorient the polymer chains of the blown film. The “orientation” of apolymer is a reference to its molecular organization, i.e., theorientation of molecules or polymer chains relative to each other. Inparticular, the extrusion process can cause the polymer chains of theblown film to be predominantly oriented in the machine direction. Asused herein predominately oriented in a particular direction means thatthe polymer chains are more oriented in the particular direction thananother direction. One will appreciate, however, that a film that ispredominately oriented in a particular direction can still includepolymer chains oriented in directions other than the particulardirection. Thus, in one or more embodiments the initial or startingfilms (films before being stretched or bonded or laminated in accordancewith the principles described herein) can comprise a blown film that ispredominately oriented in the machine direction.

The process of blowing up the tubular stock or bubble can further orientthe polymer chains of the blown film. In particular, the blow-up processcan cause the polymer chains of the blown film to be bi-axiallyoriented. Despite being bi-axially oriented, in one or more embodimentsthe polymer chains of the blown film are predominantly oriented in themachine direction (i.e., oriented more in the machine direction than thetransverse direction).

The films of one or more implementations of the present invention canhave a starting gauge between about 0.1 mils to about 20 mils, suitablyfrom about 0.2 mils to about 4 mils, suitably in the range of about 0.3mils to about 2 mils, suitably from about 0.6 mils to about 1.25 mils,suitably from about 0.9 mils to about 1.1 mils, suitably from about 0.3mils to about 0.7 mils, and suitably from about 0.4 mils and about 0.6mils. Additionally, the starting gauge of films of one or moreimplementations of the present invention may not be uniform. Thus, thestarting gauge of films of one or more implementations of the presentinvention may vary along the length and/or width of the film.

As an initial matter, one or more layers of the films described hereincan comprise any flexible or pliable material comprising a thermoplasticmaterial and that can be formed or drawn into a web or film. Asdescribed above, the film includes a plurality of layers ofthermoplastic films. Each individual film layer may itself include asingle layer or multiple layers. In other words, the individual layersof the multi-layer film may each themselves comprise a plurality oflaminated layers. Such layers may be significantly more tightly bondedtogether than the bonding provided by the purposely weak discontinuousbonding in the finished multi-layer film. Both tight and relatively weaklamination can be accomplished by joining layers by mechanical pressure,joining layers with adhesives, joining with heat and pressure, spreadcoating, extrusion coating, and combinations thereof. Adjacentsub-layers of an individual layer may be coextruded. Coextrusion resultsin tight bonding so that the bond strength is greater than the tearresistance of the resulting laminate (i.e., rather than allowingadjacent layers to be peeled apart through breakage of the laminationbonds, the film will tear).

FIG. 1A illustrates a film ply 10 a of a single layer 11. In anotherimplementation, as illustrated by FIG. 1B, a film ply 10 b can have twolayers (i.e., a bi-layered film). In particular, the film ply 10 b caninclude a first layer 11 a and a second layer 11 b. The first and secondlayers 11 a, 11 b can optionally include different grades ofthermoplastic material or include different additives, including polymeradditives. In still another implementation, shown in FIG. 1C, a film ply10 c can include three layers (i.e., a tri-layered film). For example,FIG. 1C illustrates that the film 10 c can include a first layer 11 c, asecond layer 11 d, and a third layer 11 e.

In at least one implementation, such as shown in FIG. 1C, a multilayeredfilm 10 c can include co-extruded layers. For example, the film 10 c caninclude a three-layer B:A:B structure, where the ratio of layers can be20:60:20. The exterior B layers (i.e., 11 c, 11 e) can comprise amixture of hexene LLDPE of density 0.918, and metallocene LLDPE ofdensity 0.918. The interior A core layer (11 d) can comprise a mixtureof hexene LLDPE of density 0.918, butene LLDPE of density 0.918,reclaimed resin from trash bags. Additionally, the A core layer 11 d caninclude an opacity agent. For example, the A core layer 11 d can includea colorant containing carbon black in an amount between about 0.1percent and about 6%. More particularly, the A core layer 11 d caninclude a colorant containing carbon black in an amount between about0.25 percent and about 0.75% resulting a translucent film that appearslike a gray or clouded clear film.

In another implementation, the film 10 c is a coextruded three-layerB:A:B structure, where the ratio of layers is 20:60:20. The exterior Blayers (11 c, 11 e) can comprise hexene LLDPE of density 0.918, andmetallocene LLDPE of density 0.918. The interior A core layer (11 d) cancomprise hexene LLDPE of density 0.918, metallocene LLDPE of density0.918, butene LLDPE of density 0.918, reclaimed resin from trash bags.The A core layer 11 d can also include a processing aide, colorantcontaining carbon black, and colorant containing white TiO2, resultingin a grey colored film. In some implementations, the carbon black orreclaimed resin can be omitted, resulting in a white colored film. Insuch embodiments, the A core layer 11 d can a white colorant in anamount between about 0.1 percent and about 8%. More particularly, the Acore layer 11 d can include a white colorant in an amount between about3 percent and about 7% or about 4% and about 6% resulting a white film.

In another example, the film 10 c is a coextruded three-layer B:A:Bstructure where the ratio of layers is 15:70:15. In one or moreimplementations, the LLDPE can comprise greater than 50% of the overallthermoplastic material in the film 10 c.

In another example, the film 10 c is a coextruded three-layer C:A:Bstructure where the ratio of layers is 20:60:20. The C layer 11 c cancomprise a LLDPE material with a first colorant (e.g., black). The Blayer 11 e can also comprise a LLDPE material with a second colorant(e.g., white). The LLDPE material can have a MI of 1.0 and density of0.920 g/cm3. The A core layer 11 d can comprise similar materials to anyof the core layer describe above. The A core layer 11 d can comprise awhite colorant or can be clear.

FIG. 2 illustrates a view of a multi-layer film 13 in accordance withone or more embodiments of the present invention. As shown, themulti-layer film 13 can include a first film layer 10 c and a secondfilm layer 10 c′. The first film layer 10 c and the second film layer 10c′ can include a configuration to provide the multi-layer film 13 withmaintained or decreased light transmittance despite a reduced gauge whencompared to standard films.

As shown by FIG. 2 each layer of the multi-layer film 13 can include afilm layer 10 c, 10 c′ that is a tri-layer co-extruded film as describedabove in relation to FIG. 1C. In alternative embodiments the layers ofthe multi-layer film 13 can be mono-layer, bi-layered, or include morethan three layers. In any event, the multi-layer film 13 can have onelayer 10 c with a light reflecting opacity agent and a second layer 10c′ with a light absorbing opacity agent. Furthermore, when formed in abag, the layer 10 c with the light reflecting opacity agent can bepositioned on the outside of the bag. Positioning the layer 10 c withthe light reflecting opacity agent on the outside, can decrease thelight transmittance compared to the same multi-layer film 13 in whichthe layer 10 c with the light reflecting opacity agent is on the inside.

Additionally or alternatively, the multi-layer film 13 can have onelayer 10 c with a first concentration of an opacity agent and a secondlayer 10 c′ with a second concentration of an opacity agent that is lessthat the first concentration. Furthermore, when formed in a bag, thelayer 10 c with the greater concentration of the opacity agent can bepositioned on the outside of the bag. Positioning the layer 10 c withthe greater concentration of the opacity agent on the outside, candecrease the light transmittance compared to the same multi-layer film13 in which the layer with the greater concentration of the opacityagent is on the inside.

FIG. 2 also illustrates that the layers 10 c, 10 c′ of the multi-layerfilm 13 can be at least partially separated. In other words, the layers10 c, 10 c′ of the multi-layer film 13 are separate and distinct layerthat are not co-extruded together even though each layer can include sublayers that are co-extruded. Specifically, FIG. 2 illustrates that thelayers 10 c, 10 c′ of the multi-layer film 13 are un-bonded. Inalternative embodiments, the layers 10 c, 10 c′ of the multi-layer film13 can be incrementally stretched and bonded as described below.

As previously mentioned, according to one implementation of theinvention, the separate layers of the multi-layer film arenon-continuously, lightly bonded to one another. FIGS. 3A-3B illustrateexemplary processes of partially discontinuously bonding adjacent layersof a multi-layer thermoplastic film in accordance with an implementationof the present invention to create an intermittingly bonded andstretched multi-layer film with maintained or decreased lighttransmittance. In particular, FIGS. 3A-3B illustrate an MD ring rollingprocess that partially discontinuously laminates the individual adjacentlayers of thermoplastic multi-layered film 13 by passing themulti-layered film 13 through a pair of MD intermeshing rollers 12, 14.As a result of MD ring rolling, the multi-layered film 13 is alsointermittently stretched in the machine direction MD.

As shown by the FIGS. 3A-3B, the first roller 12 and the second roller14 can each have a generally cylindrical shape. The MD intermeshingrollers 12, 14 may be made of cast and/or machined metal, such as,steel, aluminum, or any other suitable material. The MD intermeshingrollers 12, 14 can rotate in opposite directions about parallel axes ofrotation. For example, FIG. 3A illustrates that the first roller 12 canrotate about a first axis 16 of rotation in a counterclockwise direction18. FIG. 3A also illustrates that the second roller 14 can rotate abouta second axis 20 of rotation in a clockwise direction 22. The axes ofrotation 16, 20 can be parallel to the transverse direction TD andperpendicular to the machine direction MD.

The intermeshing rollers 12, 14 can closely resemble fine pitch spurgears. In particular, the MD intermeshing rollers 12, 14 can include aplurality of protruding ridges 24, 26. The ridges 24, 26 can extendalong the MD intermeshing rollers 12, 14 in a direction generallyparallel to axes of rotation 16, 20 and perpendicular to the machinedirection of the film 13 passing through the MD intermeshing rollers 12,14. Furthermore, the ridges 24, 26 can extend generally radially outwardfrom the axes of rotation 16, 20. The tips of ridges 24, 26 can have avariety of different shapes and configurations. For example, the tips ofthe ridges 24, 26 can have a rounded shape as shown in FIG. 3B. Inalternative implementations, the tips of the ridges 24, 26 can havesharp angled corners. FIGS. 3A-3B also illustrate that grooves 28, 30can separate adjacent ridges 24, 26.

The ridges 24 on the first roller 12 can be offset or staggered withrespect to the ridges 26 on the second roller 14. Thus, the grooves 28of the first roller 12 can receive the ridges 26 of the second roller14, as the MD intermeshing rollers 12, 14 intermesh. Similarly, thegrooves 30 of the second roller 14 can receive the ridges 24 of thefirst roller 12.

One will appreciate in view of the disclosure herein that theconfiguration of the ridges 24, 26 and grooves 28, 30 can preventcontact between ridges 24, 26 during intermeshing so that no rotationaltorque is transmitted during operation. Additionally, the configurationof the ridges 24, 26 and grooves 28, 30 can affect the amount ofstretching and the bond strength resulting from partially discontinuouslamination as the film passes through MD intermeshing rollers 12, 14.

Referring specifically to FIG. 3B, various features of the ridges 24, 26and grooves 28, 30 are shown in greater detail. The pitch and depth ofengagement of the ridges 24, 26 can determine, at least in part, theamount of incremental stretching and partially discontinuous laminationcaused by the MD intermeshing rollers 12, 14. As shown by FIG. 3B, thepitch 32 is the distance between the tips of two adjacent ridges on thesame roller. The “depth of engagement” (“DOE”) 34 is the amount ofoverlap between ridges 24, 26 of the different MD intermeshing rollers12, 14 during intermeshing.

The ratio of DOE 34 to pitch 32 can determine, at least in part, thebond strength provided by the partially discontinuous bonding. Accordingto one embodiment, the ratio of DOE to pitch provided by any ringrolling operation is less than about 1.1:1, suitably less than about1.0:1, suitably between about 0.5:1 and about 1.0:1, or suitably betweenabout 0.8:1 and about 0.9:1.

As shown by FIG. 3A, the direction of travel of the multi-layered film13 through the MD intermeshing rollers 12, 14 is parallel to the machinedirection and perpendicular to the transverse direction. As thethermoplastic multi-layered film 13 passes between the MD intermeshingrollers 12, 14, the ridges 24, 26 can incrementally stretch themulti-layered film 13 in the machine direction. In one or moreimplementations, stretching the multi-layered film 13 in the machinedirection can reduce the gauge of the film and increase the length ofthe multi-layered film 13. In other implementations, the multi-layeredfilm 13 may rebound after stretching such that the gauge of themulti-layered film 13 is not decreased. Furthermore, in one or moreimplementations, stretching the film 13 in the machine direction canreduce the width of the multi-layered film 13. For example, as themulti-layered film 13 is lengthened in the machine direction, the film'slength can be reduced in the transverse direction.

In particular, as the multi-layered film 13 proceeds between the MDintermeshing rollers 12, 14, the ridges 24 of the first roller 12 canpush the multi-layered film 13 into the grooves 30 of the second roller14 and vice versa. The pulling of the multi-layered film 13 by theridges 24, 26 can stretch the multi-layered film 13. The MD intermeshingrollers 12, 14 may not stretch the multi-layered film 13 evenly alongits length. Specifically, the MD intermeshing rollers 12, 14 can stretchthe portions of the film 13 between the ridges 24, 26 more than theportions of the multi-layered film 13 that contact the ridges 24, 26.Thus, the MD intermeshing rollers 12, 14 can impart or form a generallystriped pattern 36 into the multi-layered film 13. As used herein, theterms “impart” and “form” refer to the creation of a desired structureor geometry in a film upon stretching the film that will at leastpartially retain the desired structure or geometry when the film is nolonger subject to any strains or externally applied forces.

FIGS. 3A-3B illustrate that the starting or initial film 13 (i.e., thefilm that is yet to pass through the MD intermeshing rollers 12, 14) canhave a substantially flat top surface 38 and substantially flat bottomsurface 40. As seen in FIG. 3B, the multi-layer film 13 may comprise twolayers 10 c and 10 c′ that are initially separate from one another. Thefilm 13 can have an initial thickness or starting gauge 42 (i.e., thesum of 42 a and 42 b) extending between its major surfaces (i.e., thetop surface 38 and the bottom surface 40). In at least oneimplementation, the starting gauge 42, as well as the gauge 42 a, 42 bof individual layers 10 c and 10 c′ can be substantially uniform alongthe length of the multi-layer film 13. Because the inner surfaces ofeach layer 10 c and 10 c′ are somewhat tacky, the layers become lightlybonded together as they are pulled through and stretched by MDintermeshing rollers 12, 14. Those areas that are un-stretched orstretched less become lightly bonded together.

In one or more implementations, the initial film 13 need not have anentirely flat top surface 38, but may be rough or uneven. Similarly,bottom surface 40 or the inner oriented surfaces of layers 10 c and 10c′ of the film 13 can also be rough or uneven. Further, the startinggauge 42, 42 a, and 42 b need not be consistent or uniform throughoutthe entirety of pre-stretched film 13. Thus, the starting gauge 42, 42a, and 42 b can vary due to product design, manufacturing defects,tolerances, or other processing issues. According to one embodiment, theindividual layers 10 c and 10 c′ may be pre-stretched (e.g., through MDring rolling, TD ring rolling, etc.) before being positioned adjacent tothe other layer (10 c′ or 10 c, respectively). Such pre-stretching ofindividual layers can result in a striped surface exhibiting an uneventop and bottom surface similar to that seen in FIG. 3A.

FIG. 3B illustrates that films 13, can include two initially separatefilm layers 10 c-10 c′. In an alternative implementation, the film 13(and thus the resultant incrementally stretched film 10) can includethree initially separate film layers: a middle film layer and two outerfilm layers. In other embodiments, more than 3 layers may be provided(four, five, six, or more partially discontinuously or discontinuouslylaminated layers).

As seen in FIG. 3A, upon stretching and partially discontinuouslylaminating the adjacent layers, the intermittingly bonded and stretchedmulti-layer film with maintained or decreased light transmittance 15 acan include a striped pattern 36. The striped pattern 36 can includealternating series of stretched (or more stretched) regions or thinnerwebs 46 adjacent to un-stretched regions (or less stretched) or thinnerribs 44. FIG. 3B illustrates that the MD intermeshing rollers 12, 14 canincrementally stretch and partially discontinuously bond films 10 c, 10c′ to create multi-layered lightly-laminated multi-layer films 15 aincluding bonded regions or bonds 49 and un-bonded regions 47. Forexample, FIG. 3B illustrates that the film layers 10 c, 10 c′ of themulti-layered lightly-laminated film 15 a can be laminated together atthe thicker ribs 44 while the stretched (i.e., thinner) regions 46 maynot be laminated together.

In addition to any compositional differences between layers 10 c, 10 c′of a given multi-layer film, the different film layers can havediffering gauges or thicknesses. In one or more implementations, thefilm layers may be substantially equal to one another in thickness. Forexample, the inventors have found that the MD or TD tear resistance ofthe composite, multi-layer film is typically approximately equal to thelowest MD or TD tear value of the individual layers, absent any increasein tear resistance provided by weak bonding. In other words, the weakestlayer often determines the strength of the multi-layer film structure.

As shown by FIG. 3B the bonded regions 49 of the multi-layeredlightly-laminated films 15 a can have an average thickness or gauge 50a. The average gauge 50 a can be approximately equal to the combinedstarting gauges 42 a, 42 b of the starting films. In the Figures,separation between the unbonded layers at unbounded regions 47 isexaggerated for purposes of clarity. In one or more implementations, theaverage gauge 50 a can be less than the combined starting gauges 42 a-42b. The films 10 c, 10 c′ of the un-bonded regions 47 can each have anaverage thickness or gauge 42 c, 42 d. In one or more implementations,the average gauges 42 c, 42 d are less than the starting gauges 42 a, 42b. Although the un-stretched regions or thicker ribs 44 of themulti-layered lightly-laminated films may be stretched to a small degreeby MD intermeshing rollers 12,14 (or stretched in a separate operation),the un-stretched regions or thicker ribs 44 may be stretchedsignificantly less compared to the stretched regions 46.

In any event, FIGS. 3A-3B illustrate that MD intermeshing rollers 12, 14can process the initially separately layered films into MDincrementally-stretched multi-layered lightly-laminated films 15 a. Aspreviously mentioned, the MD incrementally-stretched multi-layeredlightly-laminated films 15 a can include a striped pattern 36 where thebonding occurs along a continuous line or region along the width of thefilm 15 a, parallel to the TD direction. The striped pattern 36 caninclude alternating series of un-bonded regions 47 and bonded regions49. The bonded regions 49 can comprise bonds between un-stretchedregions or thicker ribs 44 of the films 10 c, 10 c′. In other words, thebonds of the MD incrementally-stretched multi-layered lightly-laminatedfilms 15 a can be positioned directly between, be aligned with, and bondtogether un-stretched regions or thicker ribs 44. Along related lines,the un-bonded regions 47 can separate the stretched or thinner regions46.

FIG. 4 illustrates a top view of the MD incrementally-stretched andincrementally-bonded multi-layered lightly-laminated film 15 a withmaintained or decreased light transmittance. As shown by FIG. 4, thefilm 15 a includes thicker ribs 44 bonded together to form bondedregions 49 adjacent to thinner regions 46 that form un-bonded regions47. In addition to resulting in partially discontinuous lamination ofadjacent layers, MD ring rolling the film 13 can increase or otherwisemodify one or more of the tensile strength, tear resistance, impactresistance, or elasticity of the film 15 a, in addition to whateveradditional strength is provided by the partially discontinuous, lowstrength bonds between adjacent layers of the film. Such bonds can bebroken to absorb forces rather than such forces resulting in tearing ofthe film.

Furthermore, thicker ribs 44 can include bonded stripes that extendacross the film 15 a in a direction transverse (i.e., transversedirection) to a direction in which the film was extruded (i.e., machinedirection). As shown by FIG. 4, the bonded stripes or bonded regions 49can extend across the entire length of the film 15 a. One willappreciate in view of the disclosure herein that the striped pattern 36may vary depending on the method used to incrementally stretch andpartially discontinuously bond adjacent layers of film 13. To the extentthat MD or other ring rolling is used to lightly bond the film 13, thestriped pattern 36 (e.g., width and spacing of the stripes or stretchedregions 44) on the film 13 can depend on the pitch 32 of the ridges 24,26, the DOE 34, and other factors. As regions 49 represent areas of themulti-layer film in which the adjacent layers are lightly bonded to oneanother, it will be apparent that altering the spacing and/or width ofregions 49 can affect the overall strength of the film. For example,providing more bonded surface area relative to the unbonded surface areacan increase the density of such bonds that can absorb forces,increasing the film strength.

FIG. 4 further illustrates that the bonded regions 49 can beintermittently dispersed about un-bonded regions 47. In particular, eachbonded region 49 can reside between adjacent un-bonded regions 47. Alongrelated lines, each thicker rib 44 can be intermittently dispersed aboutstretched regions 46. Additionally, the bonded regions 49 and thickerribs 44 can be visually distinct from the un-bonded regions 47 andthinner regions 46 as a result of stretching. The striped pattern 36 mayvary depending on the method used to lightly laminate the film 13. Inone or more implementations, the molecular structure of thethermoplastic material of the film multi-layered 13 may be rearrangedduring stretching (e.g., particularly so during cold stretching).

One will appreciate in view of the disclosure herein that passing thefilm 13 through the MD intermeshing rollers 12, 14 to form the MDincrementally-stretched multi-layered lightly-laminated film 15 a canalso modify the orientation of the film. In particular, MD stretching apredominately MD oriented film can further orient the stretched regions46 in the machine direction. Thus, the stretched regions 46 can have anMD orientation that is greater than the MD orientation of the thickerribs 44.

MD ring rolling is one exemplary method of partially discontinuouslylaminating a multi-layer film by incremental stretching of the film. TDring rolling is another suitable method of discontinuously or partiallydiscontinuously laminating a film. For example, FIGS. 5A-5B illustratesa TD ring rolling process that partially discontinuously and lightlybonds adjacent layers of a thermoplastic multi-layer film by passing thefilm through a pair of TD intermeshing rollers 52, 54.

A TD ring rolling process (and associated TD intermeshing rollers 52,54) can be similar to the MD ring rolling process (and associated MDintermeshing rollers 12, 14) described herein above, except that theridges 56, 58 and grooves 60, 62 of the TD intermeshing rollers 52, 54extend generally orthogonally to the axes of rotation 16, 20 (i.e.,parallel to the MD direction). Thus, as shown by FIG. 5A, as thethermoplastic film 13 passes between the intermeshing rollers 52, 54,the ridges 56, 58 can incrementally stretch and lightly bond adjacentlayers of the multi-layer film 13. The resultant TDincrementally-stretched and incrementally-bonded multi-layeredlightly-laminated film 15 b with maintained or decreased lighttransmittance can include a striped pattern 36 a within the withadjacent bonded and unbonded regions.

In particular, as the films 10 c, 10 c′ proceed between the TDintermeshing rollers 52, 54, the ridges 56 of the first roller 52 canpush the films 10 c, 10 c′ into the grooves 62 of the second roller 54and vice versa. The pulling of the films 10 c, 10 c′ by the ridges 56,58 can stretch the films 10 c, 10 c′. The rollers 52, 54 may not stretchthe films 10 c, 10 c′ evenly along their length. Specifically, therollers 52, 54 can stretch the portions of the films 10 c, 10 c′ betweenthe ridges 56, 58 more than the portions of the films 10 c, 10 c′ thatcontact the ridges 56, 58, or vice versa. Thus, the rollers 52, 54 canimpart or form a ribbed pattern 36 a into resultant multi-layered film.

The TD intermeshing rollers 52, 54 can form thick regions or thickerribs 44 a, thinner webs 46 a, and bonds 49 a in the films 10 c, 10 c′.In one or more implementations, the adjacent thick ribs 44 a of thefilms 10 c, 10 c′ can be joined by bonds 49 a. In addition to formingribs 46 a, 44 a and bonds 49 a, TD ring rolling the films 10 c, 10 c′can increase or otherwise modify one or more of the tensile strength,tear resistance, impact resistance, or elasticity of the films 10 c, 10c′, in addition to whatever additional strength is provided by thepartially discontinuous, bonds 49 a between adjacent layers.

To the extent that TD or other ring rolling is used to lightly bond thefilms 10 c, 10 c′, the ribbed pattern 36 a (e.g., width and spacing ofthe ribs 46 a, 44 a) can depend on the pitch 32 a of the ridges 56, 58,the DOE 34 a, and other factors. As portions of the films 10 c, 10 c′including a ribbed pattern 36 a also represent areas of the multi-layerfilm in which the adjacent layers are non-continuously bonded to oneanother, it will be apparent that altering the spacing and/or width ofribs 46 a, 44 a can affect the overall strength of the film. Forexample, providing more bonded surface area relative to the unbondedsurface area can increase the density of such bonds 49 a that can absorbforces, increasing the film strength.

FIG. 5B further illustrates that the bonds 49 a can bond thick linearribs 44 a of the layers 10 c, 10 c′ together. In particular, the bonds49 a can be coextensive and aligned with opposing thicker ribs 44 a andbond them together. FIG. 5B illustrates that the bonds 49 a can securesome, but not all, of the thick linear ribs 44 a of one layer to thethick linear ribs 44 a of an adjacent layer. In particular, FIG. 5Billustrates that bonds 49 a can secure every other thick linear rib 44 aof adjacent layers together. The unbounded thicker ribs 44 a can formunbounded regions 45. In alternative implementations, bonds 49 a cansecure each thick linear rib 44 a of adjacent layer together.

FIG. 6 illustrates a top view of the TD incrementally-stretched andincrementally-bonded multi-layered lightly-laminated film 15 b withmaintained or decreased light transmittance. As shown by FIG. 6, thefilm 15 b includes thicker ribs 44 a bonded together to form bondedregions 49 a adjacent to thinner regions 46 a that form un-bondedregions 47 a with bonded regions 46 a and adjacent un-bonded regions 44a. Similar to MD ring rolling, TD ring rolling the multi-layered film 13can result in relatively light, partially discontinuous bonding ofadjacent layers 10 c, 10 c′, increasing the strength of the multi-layerfilm 15 b.

FIG. 6 illustrates that the bonded regions 49 a can include stripes thatextend across the multi-layered lightly-laminated film 15 b in themachine direction. As shown by FIG. 6, the stripes or bonded regions 49a can extend across the entire width of the multi-layeredlightly-laminated film 15 b. In alternative implementations, bondedregions 49 a can extend across only a portion of the multi-layeredlightly-laminated film 15 b. Similar to MD ring rolling, the pitch andthe DOE of the ridges 56, 58 of the intermeshing rollers 52, 54 canaffect the width and spacing of the stripes or bonded regions 49 a, aswell as the strength of the weak bonds formed between adjacent layers,thereby affecting the overall increase in strength provided by theprocessing.

In still further implementations, a multi-layered film 13 can undergoboth an MD ring rolling process and a TD ring rolling process to lightlybond the individual layers together. For example, FIG. 7 illustrates atop view of a MD & TD incrementally-stretched and incrementally-bondedmulti-layered lightly-laminated film 15 c with maintained or decreasedlight transmittance. The film 15 c includes thicker ribs 44 b, 44 cbonded together to form bonded regions 49 b, 49 c adjacent to thinnerregions 46 b that form un-bonded regions 47 b. The multi-layeredlightly-laminated film 15 c can have a grid pattern 36 b includingalternating series of un-bonded regions 47 b and bonded regions 49 b, 49c. In particular, un-bonded regions 47 b may comprise a plurality ofdiscrete squares or rectangles while the remainder of the surfacecomprises a grid of horizontal and vertical bonded regions that areconnected together. The bonded regions 49 b, 49 c can include stripes 49b that extend along the multi-layered lightly-laminated film 15 c in themachine direction, and stripes 49 c that extend along the film in thetransverse direction, which cross each other. As shown by FIG. 7, in oneor more implementations, the aspect ratio of the rows and columns of thebonded regions 49 b, 49 c can be approximately 1 to 1. In alternativeimplementations, the aspect ratio of the rows and columns of -bondedregions 49 b, 49 c can be greater or less than 1 to 1, for example, asexplained in greater detail in relation to FIG. 13.

The multi-layered lightly-laminated film 15 c with bonded regions andadjacent un-bonded regions created by MD and TD ring rolling can allowfor greater material savings by further increasing the surface area of agiven portion of film, by increasing the density of light laminationbonds within a given area, and may also provide properties or advantagesnot obtained by MD or TD ring rolling alone.

In yet further implementations, a manufacturer can use diagonal orhelical (DD) ring rolling to lightly bond a thermoplastic film. DD ringrolling processes (and associated DD intermeshing rollers) can besimilar to the MD ring rolling process (and associated MD intermeshingrollers 12, 14) described herein above, except that the ridges andgrooves of the DD intermeshing rollers can extend at an angle relativeto the axes of rotation. In particular, the ridges and grooves of the DDring rollers can extend at an angle of between about 15 degrees andabout 75 degrees relative to the axes of rotation (or the MD or TDdirections). FIG. 8 illustrates a DD incrementally-stretched andincrementally-bonded multi-layered lightly-laminated film 15 d withmaintained or decreased light transmittance formed by lightly bondingtwo films together by passing the films through DD ring rollers. Asshown the multi-layered lightly-laminated film 15 d can have a diamondpattern 36 c. The diamond pattern 36 c can include alternating series ofdiamond-shaped thinner regions 46 c defining un-bonded areas or regions47 c and thicker ribs 44 a secured by bonds to form bonded regions 49 d.The bonded regions can include stripes 49 d oriented at an anglerelative to the transverse direction such that the stripes 49 d areneither parallel to the transverse or machine direction. The illustratedconfiguration may be achieved with two ring rolling operations, similarto that of FIG. 7, but in which the DD ring rollers of each operationare angularly offset relative to one another (e.g., one providing anangle of about 45° off of MD ring rolling, the other providing an angleof about 45° off of TD ring rolling). One will appreciate that DD ringrolling the film can biaxially orient the thinner, stretched regions 46c. In particular, orient the thinner, stretched regions 46 c at an angleto the machine direction and the transverse direction.

In accordance with another implementation, a structural elastic likefilm (SELF) process may be used to create a thermoplastic film withstrainable networks, which similarly results in discontinuous bonding ofadjacent layers within a multi-layer film. As explained in greaterdetail below, the strainable networks can include adjacent bonded andun-bonded regions. U.S. Pat. Nos. 5,518,801; 6,139,185; 6,150,647;6,394,651; 6,394,652; 6,513,975; 6,695,476; U.S. Patent ApplicationPublication No. 2004/0134923; and U.S. Patent Application PublicationNo. 2006/0093766 each disclose processes for forming strainable networksor patterns of strainable networks suitable for use with implementationsof the present invention. The contents of each of the aforementionedpatents and publications are incorporated in their entirety by referenceherein.

FIG. 9 illustrates a pair of SELF'ing intermeshing rollers 72, 74 forcreating strainable networks with lightly bonded regions in a film. Thefirst SELF'ing intermeshing roller 72 can include a plurality of ridges76 and grooves 78 extending generally radially outward in a directionorthogonal to an axis of rotation 16. Thus, the first SELF'ingintermeshing roller 72 can be similar to a TD intermeshing roller 52,54. The second SELF'ing intermeshing roller 74 can include also includea plurality of ridges 80 and grooves 82 extending generally radiallyoutward in a direction orthogonal to an axis of rotation 20. As shown byFIG. 9, however, the ridges 80 of the second SELF'ing intermeshingroller 74 can include a plurality of notches 84 that define a pluralityof spaced teeth 86.

Referring now to FIG. 10, a multi-layered lightly-laminated film 15 ewith bonded regions dispersed about un-bonded regions created using theSELF'ing intermeshing rollers 72, 74 is shown. In particular, as thefilm passes through the SELF'ing intermeshing rollers 72, 74, the teeth86 can press a portion of the multi-layer web or film out of plane tocause permanent deformation of a portion of the film in the Z-direction.The portions of the film that pass between the notched regions 84 of theteeth 86 will be substantially unformed in the Z-direction, resulting ina plurality of deformed, raised, rib-like elements 88. The length andwidth of rib-like elements 88 depends on the length and width of teeth86.

As shown by FIG. 10, the strainable network of the multi-layeredlightly-laminated film 15 e can include first thicker regions 44 e,second thicker regions 44 f, stretched, thinner transitional regions 46d connecting the first and second thicker regions 44 e, 44 f The firstthicker regions 44 e and the stretched, thinner regions 46 d can formthe raised rib-like elements 88 of the strainable network. In one ormore embodiments, the rib-like elements 88 can comprise bonded regions49 e can be discontinuous or separated as they extend across themulti-layered film 15 e in both transverse and machine directions. Thisis in contrast to stripes that extend continuously across a film in oneof the machine or transverse directions.

The rib-like elements 88 can allow the multi-layered lightly-laminatedfilm 15 e to undergo a substantially “geometric deformation” prior to a“molecular-level deformation.” As used herein, the term “molecular-leveldeformation” refers to deformation, which occurs on a molecular leveland is not discernible to the normal naked eye. That is, even though onemay be able to discern the effect of molecular-level deformation, e.g.,elongation or tearing of the film, one is not able to discern thedeformation, which allows or causes it to happen. This is in contrast tothe term “geometric deformation,” which refers to deformations ofmulti-layered lightly-laminated film 15 e that are generally discernibleto the normal naked eye when the multi-layered film 15 e or articlesembodying the multi-layered lightly-laminated film 15 e are subjected toan applied strain. Types of geometric deformation include, but are notlimited to bending, unfolding, and rotating.

Thus, upon application of strain, the rib-like elements 88 can undergogeometric deformation before either the rib-like elements 88 or the flatregions undergo molecular-level deformation. For example, an appliedstrain can pull the rib-like elements 88 back into plane with the flatregions prior to any molecular-level deformation of the multi-layeredfilm 15 e. Geometric deformation can result in significantly lessresistive forces to an applied strain than that exhibited bymolecular-level deformation.

In addition to improved properties thus provided by the ability togeometrically deform, the SELF'ing process also discontinuously andlightly laminates adjacent layers of the multi-layer film together,providing the benefits noted above. In particularly, the film layers 10c, 10 c′ can be lightly laminated at regions 49 e, but un-bonded atregions 47 d. The strength of the lamination bond is relatively weak, soas to be less than the weakest tear resistance of the individual layersof the multi-layer film. Thus, the lamination bond is broken rather thanthe individual layer tearing upon application of a force. Typically,tearing in the MD direction requires less applied force than tearing inthe TD direction, thus in one embodiment, the lamination bond strengthis less than the MD tear resistance of each individual layer of themulti-layer film.

FIG. 11 illustrates a multi-layered lightly-laminated film 15 f with astrainable network of rib-like elements 88 a arranged in diamondpatterns. The strainable network of the multi-layered lightly-laminatedfilm 15 f can include first thicker regions 44 e, second thicker regions44 f, stretched, thinner transitional regions 46 d connecting the firstand second thicker regions 44 e, 44 f. The first thicker regions 44 eand the stretched, thinner regions 46 d can form the raised rib-likeelements 88 a of the strainable network. In one or more embodiments, therib-like elements 88 a can comprise bonded regions 49 e.

One or more implementations of the present invention can includestrainable network patterns other than those shown by FIGS. 10 and 11,or combinations of various patterns. It should be understood that theterm “pattern” is intended to include continuous or discontinuoussections of patterns, such as may result, for example, from theintersection of first and second patterns with each other. Furthermore,the patterns can be aligned in columns and rows aligned in the machinedirection, the transverse direction, or neither the machine nortransverse directions.

One will appreciate in view of the disclosure herein that using ringrolling and/or SELFing to form the weak bonds can provide the additionalbenefit of stretching the film layers, thereby reducing the basis weightof the multi-layered lightly-laminated film. Thus, using incrementalstretching to form the weak bonds can allow for multi-layer films at alower basis weight (amount of raw material) to perform the same as orbetter than higher basis weight mono-layer or co-extruded films.

In addition to ring rolling and SELFing, one or more implementationsinclude using embossing, stamping, adhesive lamination, ultrasonicbonding, or other methods of lightly laminating layers of a multilayerfilm. In such implementations, one or more of the layers of themulti-layered lightly-laminated film can be stretched to reduce thebasis weight and/or modify the strength parameters of the film prior tolamination. Stretching of the individual layers can includeincrementally-stretching (e.g., ring rolling, SELFing) or continuousstretching (e.g., MDO).

As alluded to earlier, including differing opacity agents in layers of amulti-layer can maintain or decrease light transmittance of themulti-layer film despite a reduction in gauge and an overall reductionof opacity agents. The following example presents the results of aseries of tests performed on thermoplastic films. These examples areillustrative of the invention claimed herein and should not be construedto limit in any way the scope of the invention.

EXAMPLES

In examples 1-12 each of the films are hexene linear-low densitypolyethylene and the list percentages of opacity agents (i.e., masterbatch white or black). Thus, if a film is noted as having 6% masterbatchin the core, the film would also include 94% hexene LLDPE in the coreand 100% hexene LLDPE in the skins. Similarly if a film is noted ashaving 0.50 masterbatch in the skins, the film would also include 99.50%hexene LLDPE in the skins and 100% hexene LLDPE in the core.

In a first example, a 0.45 mil, three-layer film with a 20:60:20 layerratio containing 6% white masterbatch in the core layer was extruded(i.e., white layer). Separately, a 0.45 mil, three layer film with a20:60:20 layer ratio containing 0.75% carbon black masterbatch in theskin layers was extruded (i.e., black layer). While the second film isreferred to herein as a black layer, one will appreciate in view of thedisclosure herein that due to the small amount of carbon blackmasterbatch, the “black layer” appears like a cloudy gray clear ortransparent film. The two films were discontinuously laminated by havingthe black C-folded web inserted into the white C-folded web followed byMD ring rolling at 190 DOE with a 200 pitch tool and then TD ring rolledat 30 DOE with a 40 pitch tool. The gauge by weight of the laminatedstructure was measured to be 0.73 mils. The light transmission of thislaminated structure (herein referred to as structure 1A) was measuredusing a BYK Garner Haze-Gard Plus unit following ASTM D-1003 (Haze andLuminous Transmittance of Transparent Plastics) and found to be 61.9%.The total white masterbatch concentration of this structure is 1.80%.

In a second example, the same two base films of Example 1 werediscontinuously laminated at the same conditions, but with the whiteC-folded web inserted into the black C-folded web. The gauge-by-weightof the laminated structure (herein referred to as structure 1B) wasessentially the same as laminated structure 1A (measured to be 0.72mils), but the light transmission increased to 66.2%. The total whitemasterbatch concentration of this structure is 1.80%.

In a third example, a 0.45 mil, three-layer film with a 20:60:20 layerratio containing 6% white masterbatch in the core layer was extruded(i.e., white layer). Separately, a 0.45 mil, three layer film with a20:60:20 layer ratio containing 0.50% carbon black masterbatch in theskin layers was extruded (i.e., black layer). The two films werediscontinuously laminated by having the black C-folded web inserted intothe white C-folded web followed by MD ring rolling at 190 DOE with a 200pitch tool and then TD ring rolled at 30 DOE with a 40 pitch tool. Thegauge-by-weight of the laminated structure (herein referred to asstructure 2A) was measured to be 0.74 mils. The light transmission ofthis laminated structure was measured and found to be 64.9%. The totalwhite masterbatch concentration of this structure is 1.80%.

In a fourth example, the same two base films of Example 3 werediscontinuously laminated at the same conditions, but with the whiteC-folded web inserted into the black C-folded web. The gauge-by-weightof the laminated structure (herein referred to as structure 2B) wasessentially the same as laminated structure 2A (measured to be 0.76mils), but the light transmission increased to 70.0%. The total whitemasterbatch concentration of this structure is 1.80%.

In a fifth example, a 0.45 mil, three-layer film with a 20:60:20 layerratio containing 6% white masterbatch in the core layer was extruded(i.e., white layer). Separately, a 0.45 mil, three-layer film with a20:60:20 layer ratio containing 0.25% carbon black masterbatch in theskin layers was extruded (i.e., black layer). The two films werediscontinuously laminated by having the black C-folded web inserted intothe white C-folded web followed by MD ring rolling at 190 DOE with a 200pitch tool and then TD ring rolled at 30 DOE with a 40 pitch tool. Thegauge-by-weight of the laminated structure (herein referred to asstructure 3A was measured to be 0.75 mils. The light transmission ofthis laminated structure was measured and found to be 66.9%. %. Thetotal white masterbatch concentration of this structure is 1.80%

In a sixth example, the same two base films of Example 5 werediscontinuously laminated at the same conditions, but with the whiteC-folded web inserted into the black C-folded web. The gauge-by-weightof the laminated structure (herein referred to as structure 3B) was thesame as the laminated structure 3A (measured to be 0.75 mils), but thelight transmission increased to 71.2%. The total white masterbatchconcentration of this structure is 1.80%.

In a seventh example, a 0.45 mil, three-layer film with a 20:60:20 layerratio containing 4% white masterbatch in the core layer was extruded(i.e., white layer). Separately, a 0.45 mil, three-layer film with a20:60:20 layer ratio containing 0.75% carbon black masterbatch in theskin layers was extruded (i.e., black layer). The two films werediscontinuously laminated by having the black C-folded web inserted intothe white C-folded web followed by MD ring rolling at 190 DOE with a 200pitch tool and then TD ring rolled at 30 DOE with a 40 pitch tool. Thegauge-by-weight of the laminated structure was measured to be 0.72 mils.The light transmission of this laminated structure (herein referred toas structure 4A) was measured and found to be 64.5%. The total whitemasterbatch concentration of this structure is 1.2%.

In a eighth example, the same two base films of Example 7 werediscontinuously laminated at the same conditions, but with the whiteC-folded web inserted into the black C-folded web. The gauge-by-weightof the laminated structure (herein referred to as structure 4B) wasessentially the same as the laminated structure 4A (measured to be 0.73mils), but the light transmission increased to 69.7%. The total whitemasterbatch concentration of this structure is 1.2%.

In a ninth example, a 0.45 mil, three-layer film with a 20:60:20 layerratio containing 4% white masterbatch in the core layer was extruded(i.e., while layer). Separately, a 0.45 mil, three-layer film with a20:60:20 layer ratio containing 0.50% carbon black masterbatch in theskin layers was extruded (i.e., black layer). The two films werediscontinuously laminated by having the black C-folded web inserted intothe white C-folded web followed by MD ring rolling at 190 DOE with a 200pitch tool and then TD ring rolled at 30 DOE with a 40 pitch tool. Thegauge-by-weight of the laminated structure (herein referred to asstructure 5A) was measured to be 0.75 mils. The light transmission ofthis laminated structure was measured and found to be 69.7%. The totalwhite masterbatch concentration of this structure is 1.2%.

In a tenth example, the same two base films of Example 9 werediscontinuously laminated at the same conditions, but with the whiteC-folded web inserted into the black C-folded web. The gauge-by-weightof the laminated structure (herein referred to as structure 5B) wasslightly thicker than same as the laminated structure 5A (measured to be0.77 mils), but the light transmission increased to 72.8%. The totalwhite masterbatch concentration of this structure is 1.2%.

In an eleventh example, a 0.45 mil, three-layer film with a 20:60:20layer ratio containing 4% white masterbatch in the core layer wasextruded (i.e., white layer). Separately, a 0.45 mil, three-layer filmwith a 20:60:20 layer ratio containing 0.25% carbon black masterbatch inthe skin layers was extruded (i.e., black layer). The two films werediscontinuously laminated by having the black C-folded web inserted intothe white C-folded web followed by MD ring rolling at 190 DOE with a 200pitch tool and then TD ring rolled at 30 DOE with a 40 pitch tool. Thegauge-by-weight of the laminated structure (herein referred to asstructure 6A) was measured to be 0.76 mils. The light transmission ofthis laminated structure was measured and found to be 71.7%. The totalwhite masterbatch concentration of this structure is 1.2%.

In a twelfth example, the same two base films of Example 11 werediscontinuously laminated at the same conditions, but with the whiteC-folded web inserted into the black C-folded web. The gauge-by-weightof the laminated structure (herein referred to as structure 6B) wasessentially the same as the laminated structure 6A (measured to be 0.75mils), but the light transmission increased to 76.0%. The total whitemasterbatch concentration of this structure is 1.2%.

Table 1 lists properties of these films along with the properties of acontrol film. The control film is a 0.90 mil thermoplastic film. Thecontrol film is a co-extruded 20:60:20 layer ratio containing 5% whitemasterbatch (white pigment) in the core layer. The total concentrationof white masterbatch for the control film is 3.0%. The total lighttransmittance is 72%. The control film is a common film used in trashbags. The control film is considered a quality film in terms of strengthand light transmittance.

TABLE 1 Structure GBW Total While Light Outer Outer Layer Inner InnerLayer ID (mils) Conc. (%) Trans. (%) Haze (%) Layer Pigment Conc. (%)Layer Pigment Conc. (%) Control 0.90 3.0 72.00 White 5.00 n/a n/a 1A0.73 1.80 61.90 90.10 White 6.00 Black 0.75% 1B 0.72 1.80 66.20 91.00Black 0.75 White 6.00% 2A 0.74 1.80 64.90 91.40 White 6.00 Black 0.50%2B 0.76 1.80 70.00 91.80 Black 0.50 White 6.00% 3A 0.75 1.80 66.90 91.50White 6.00 Black 0.25% 3B 0.75 1.80 71.20 92.10 Black 0.25 White 6.00%4A 0.72 1.20 64.50 87.20 White 4.00 Black 0.75% 4B 0.73 1.20 69.70 87.10Black 0.75 White 4.00% 5A 0.75 1.20 69.70 87.50 White 4.00 Black 0.50%5B 0.77 1.20 72.80 88.10 Black 0.50 White 4.00% 6A 0.76 1.20 71.70 87.50White 4.00 Black 0.25% 6B 0.75 1.20 76.00 88.30 Black 0.25 White 4.00%

The results from Table 1 indicate that some of theincrementally-stretched and discontinuously-laminated films undercertain conditions can have a maintained or decreased lighttransmittance compared to the control film despite a reduction in bothgauge and overall opacity agents. In particular, as shown in Table 1,the incrementally-stretched and discontinuously-laminated films weregenerally 20% thinner and contained between 40% and 60% less whitepigment compared to the control film. Nonetheless, several of theincrementally-stretched and discontinuously-laminated films hadmaintained or decreased light transmittance compared to the controlfilm. One will appreciate in view of the disclosure herein that thereduction of material and pigment provided by incrementally-stretchedand discontinuously-laminated films of one or more embodiments canprovide a considerable advantage over conventional films.

Additionally, the results from Table 1 further illustrate that the orderof the layers containing the different opacity layers can play asignificant, yet unexpected role in the light transmittance of theresultant incrementally-stretched and discontinuously-laminated films.In particular, Table 1 shows that when the outer layer contains thelight reflecting opacity agent (e.g., white pigment) and inner layercontains the light absorbing opacity agent (e.g., black pigment), thelight transmittance unexpectedly was lower than when the outer layerincluded the light absorbing opacity agent.

Table 2 shown below illustrates the light transmittance, haze, and gaugeof the individual layers of film user to create the laminate structuresincluded in Table 1. Table 2 includes values for the plies or layers offilm both in an un-stretched state and a stretched state.

TABLE 2 Single Plies Single Plies Un-Stretched Stretched Light MD TDEst. Light Ply Gauge Trans Haze DOE DOE Gauge Trans Haze Pigment ID ID(Mils) (%) (%) (Mils) (Mils) (Mils) (%) (%) Conc. 1A I 0.45 73.20 85.40190 30 0.37 80.50 80.40 6.00% White II 0.45 80.50 43.70 0.37 82.50 56.300.75% Black 1B II 0.45 80.50 43.70 190 30 0.36 82.80 56.30 0.75% Black I0.45 73.20 85.40 0.36 80.10 80.30 6.00% White 2A I 0.45 73.20 85.40 19030 0.37 79.50 81.50 6.00% White III 0.45 84.60 44.90 0.37 86.90 58.800.50% Black 2B III 0.45 84.60 44.90 190 30 0.38 86.60 58.00 0.50% BlackI 0.45 73.20 85.40 0.38 80.00 79.70 6.00% White 3A I 0.45 73.20 85.40190 30 0.38 79.70 81.70 6.00% White IIII 0.45 88.40 39.60 0.38 89.0059.20 0.25% Black 3B IIII 0.45 88.40 39.60 190 30 0.38 88.70 58.00 0.25%Black□ I 0.45 73.20 85.40 0.38 78.60 82.80 6.00% White 4A V 0.45 81.2073.90 190 30 0.36 83.40 74.60 4.00% White II 0.45 80.50 43.70 0.36 82.5056.00 0.75% Black 4B V 0.45 80.50 43.70 190 30 0.37 82.80 53.40 0.75%Black□ II 0.45 81.20 73.90 0.37 83.40 74.20 4.00% White 5A V 0.45 81.2073.90 190 30 0.38 83.90 73.60 4.00% White III 0.45 84.60 44.90 0.3887.20 58.40 0.50% Black 5B III 0.45 84.60 44.90 190 30 0.39 86.70 57.800.50% Black□ V 0.45 81.20 73.90 0.39 82.70 75.80 4.00% White 6A V 0.4581.20 73.90 190 30 0.38 83.90 73.50 4.00% White IIII 0.45 88.40 39.600.38 88.90 57.10 0.25% Black 6B IIII 0.45 88.40 39.60 190 30 0.38 89.1058.00 0.25% Black V 0.45 81.20 73.90 0.38 84.00 73.30 4.00% White

As shown by Table 2 incrementally stretching the films both reduces thegauge and increases the light transmittance. The increase in lighttransmittance is expected in the incrementally stretched films becausethe films are thinner.

One will appreciate in view of the disclosure herein that the lightlybonded multi-layered films described above can form part of any type ofproduct made from, or incorporating, thermoplastic films. For instance,grocery bags, trash bags, sacks, packaging materials, feminine hygieneproducts, baby diapers, adult incontinence products, sanitary napkins,bandages, food storage bags, food storage containers, thermal heatwraps, facial masks, wipes, hard surface cleaners, and many otherproducts can include lightly bonded multi-layer films to one extent oranother. The films and methods of the present invention may particularlybenefit trash bags and food storage bags.

Referring to FIG. 12, the multi-layer film 15 b with maintained ordecreased light transmittance illustrated in FIG. 6 is incorporated in aflexible draw tape bag 100. The bag 100 can include a bag body 92 formedfrom a piece of incrementally-stretched adhesively-laminated film 15 bfolded upon itself along a bag bottom 94. Side seams 96 and 98 can bondthe sides of the bag body 92 together to form a semi-enclosed containerhaving an opening 90 along an upper edge 102. The bag 100 alsooptionally includes closure means 104 located adjacent to the upper edge102 for sealing the top of the bag 100 to form a fully-enclosedcontainer or vessel. The bag 100 is suitable for containing andprotecting a wide variety of materials and/or objects. The closure means104 can comprise flaps, adhesive tapes, a tuck and fold closure, aninterlocking closure, a slider closure, a zipper closure or otherclosure structures known to those skilled in the art for closing a bag.

As shown, the sides of the bag body 92 can include two film layers withthicker regions 44 a that are bonded 49 a and stretched regions 46 athat are un-bonded. Both the bonded, thicker regions 44 a, 49 a and thestretched, unbounded regions 46 a, 47 a can form of stripes. The stripescan extend across the multi-layered bag 100 in the MD direction, or inother words, from the first side seam 96 to the second side seam 98. Themulti-layered bag 100 can require less material to form than anidentical bag formed with film 13 (not discontinuouslylaminated/incrementally stretched) of the same thermoplastic material.Additionally, despite requiring less material, the multi-layered bag 100includes improved strength properties imparted by lightly bondingadjacent layers of the multi-layer film together. Additionally, despiterequiring less material, the bag 100 can have the same or lesser lighttransmittance than an identical bag formed with an un-stretched film ofthe same thermoplastic material. The maintained or decreased lighttransmittance can cause the bag 90 to appear thicker and stronger.Additionally, the maintained or decreased light transmittance canprevent or reduce the ability to see the contents within the bag 100.

Furthermore, a bag 100 formed from a multi-layered lightly-laminatedfilm can have a first layer of thermoplastic material. The first layercan include first and second side walls joined along a bottom edge, afirst side edge, and an opposing second side edge. In particular, thebottom edge of the first layer can comprise a fold. The bag 100 can alsoinclude a second layer of thermoplastic material. The second layer caninclude including first and second side walls joined along a bottomedge, a first side edge, and an opposing second side edge. The secondlayer is positioned within the first layer. Furthermore, the first andthe second layer are weak bonded to each other and incrementallystretched.

In one or more implementations, as mentioned above, the outer layer ofthe bag (e.g., any of bags 100-100 h) can comprise a film with a firstopacity agent. In particular, in one or more embodiments the firstopacity agent can comprise a white pigment. The inner layer of the bagcan comprise a second film with a second opacity agent differing fromthe first opacity agent. In particular, in one or more embodiments thesecond opacity agent can comprise a black pigment. The inner layer canhave a blurry or gray transparent appearance due to the inclusion ofonly a small amount of black pigment. When viewed from the outside thebag can appear off-white. The combination of the inner and outer layersof the bag (e.g., any of bags 100-100 h) with the differing opacityagents can provide the bag (e.g., any of bags 100-100 h) with decreasedor maintained light transmittance despite a reduction in gauge and anoverall amount of opacity agents.

FIG. 13 illustrates a multi-layered tie bag 100 a incorporating amulti-layered lightly-laminated film in accordance with animplementation of the present invention. As shown, the sides of the tiebag 100 a can include a pattern of un-bonded, regions 47 f and bondedregions 49, 49 a created by MD and TD ring rolling. The lightly bondedregions can include stripes that extend across the bag 100 a in themachine direction. Additionally, the bonded regions can include stripesthat extend across the bag 100 a in the transverse direction, or inother words from the bag bottom 108 to flaps 110 of an upper edge 112 ofthe multi-layered bag 100 a. Bonded regions 49, 49 a are characterizedby relatively weak bonding of adjacent layers of the multi-layer film,which acts to absorb forces into breaking of the lamination bond ratherthan allowing that same force to cause tearing of either of the layersof the multi-layer film. Such action provides significantly increasedstrength to the multi-layer film as compared to a monolayer similarthickness film or compared to a multi-layer film of similar thicknesswhere the layers are strongly bonded together (i.e., at a bond strengthat least as great as the tear resistance of the weakest layer). Thelamination bond includes a bond strength that is advantageously lessthan the tear resistance of each of the individual films so as to causethe lamination bond to fail prior to tearing of the film layers.

In comparison with the film 15 c of FIG. 7, the spacing between the MDextending thicker ribs or regions 44 a are greater in the multi-layeredbag 100 a. Using MD ring rolls having a greater pitch between ridgescreates this effect. Similarly, the spacing of the TD extending thickerribs 44 is greater in the multi-layered bag 100 a than the multi-layeredfilm 15 c. Using TD ring rolls having a greater pitch between ridgescreates this effect. Furthermore, the relative spacing between the MDextending stripes and the TD extending stripes differs in themulti-layered bag 100 a, while relative spacing is the same in themulti-layered film 15 c. This effect is created by using TD ring rollshaving a greater pitch between ridges compared to the pitch betweenridges of the MD ring rolls.

One will appreciate in view of the disclosure herein that the use ofintermeshing rollers with greater or varied ridge pitch can provide thedifferent spacing and thicknesses of the stripes. Thus, a manufacturercan vary the ridge pitch of the intermeshing rollers to vary the patternof the multi-layer film. The bond density (i.e., the fraction of surfacearea that is bonded relative to unbonded) and particular patternprovided not only affects the aesthetic appearance of the bag or film,but may also affect the strength characteristics provided. For example,higher bond density may provide increased strength as it provides agreater number of relatively low strength lamination bonds that may bebroken so as to absorb forces, preventing such forces from leading totearing of the bag or film. Film 15 c of FIG. 7 has a higher bonddensity than the film of the bag 100 a of FIG. 13.

By way of further example, where the MD tear resistance is lower than TDtear resistance for the particular films employed, it may beadvantageous to provide a higher density of bonds in the MD than the TDdirection. This may provide greater improvement to MD tear resistance ofthe multi-layered lightly-laminated film as compared to TD tearresistance improvement. A similar configuration could be provided forfilms in which the TD tear resistance was lower than MD tear resistanceby increasing bond density in the TD direction.

In addition to varying the pattern of bonded and un-bonded regions in abag or film, one or more implementations also include providing lightlybonded regions in certain sections of a bag or film, and only un-bonded(or alternatively tightly bonded) regions in other sections of the bagor film. For example, FIG. 14 illustrates a multi-layered bag 100 bhaving an upper section 116 adjacent a top edge 118 that is devoid ofbonded regions. Similarly, the multi-layered bag 100 b includes a bottomsection 120 adjacent a bottom fold or edge 122 devoid of bonded regions.In other words, both the top section 116 and bottom section 120 of themulti-layered bag 100 b can each consist only of un-bonded regions.Alternatively, the layers of sections 116 and 120 may be tightly bondedtogether (e.g., co-extruded). In any case, sections 116 and 120 may bevoid of bonds.

A middle section 124 of the multi-layered bag 100 b between the upperand lower sections 116, 120 on the other hand can include lightly bondedregions interspersed with un-bonded regions. In particular, FIG. 14illustrates that the middle section can include a strainable network ofrib-like elements arranged in diamond patterns similar to themulti-layered lightly-laminated film 15 f of FIG. 11. Thus, the middlesection 124 of the multi-layered bag 100 b can include improved strengthcreated by the weak bonds of the strainable network.

In one or more additional implementations the present invention includesproviding different lightly bonded regions in different sections of abag or film. For example, FIG. 15 illustrates a multi-layered bag 100 csimilar to the multi-layered bag 100 b of FIG. 14, except that thebottom section 120 a includes alternating series of stretched, un-bondedregions 46 a, 47 a and thicker bonded regions 44 a, 49 a created by TDring rolling. Thus, the middle section 124 of the bag 100 c can includeproperties of increased strength as a result of light discontinuouslamination and increased elasticity through geometric deformation, whilethe bottom section includes increased strength as a result of lightpartially discontinuous lamination by TD ring rolling.

Thus, one will appreciate in view of the disclosure herein that amanufacturer can tailor specific sections or zones of a bag or film withdesirable properties by MD ring rolling, TD ring rolling, DD ringrolling, SELFing, or a combination thereof. One region of the bag mayinclude a first type of incremental stretching to modify the strengthparameters and light transmittance, while a second region includes asecond type of incremental stretching designed to reduce gauge andmaintain or decrease the light transmittance or modify the strengthparameters. Thus, a manufacturer can provide any region of a bag withthe different incrementally-stretched films and their associatedproperties described herein above.

FIG. 16 illustrates yet another multi-layered bag 100 d including anupper section 116 a adjacent a top edge 118 that includes alternatingseries of thicker, bonded regions 44 b, 49 b and stretched, thinnerun-bonded regions 46 b, 47 b created by MD and TD ring rolling similarto the film 15 c of FIG. 7. Furthermore, the middle section 124 a of themulti-layered bag 126 can include thicker, bonded regions 44, 49 andstretched, thinner, un-bonded regions 46, 47 in the form of stripescreated by MD ring rolling.

FIG. 17 illustrate yet another multi-layered bag 100 e. Themulti-layered bag 100 e is formed from a MD incrementally-stretchedmulti-layered lightly-laminated film 15 a, such as that of FIG. 4. Thebag 100 e can include an inner layer 10 c and an outer layer 10 c′ thatare lightly bonded together by bonds 49. Additionally, a hem seal 126(to hold in the draw string 104) and side seals (i.e., seals at sideedges 96 and 98) can additionally secure the inner layer 10 c to theouter layer 10 c′. A bottom fold 94 can be positioned opposite a topedge 102.

The thicker ribs 44 can include bonded stripes that extend across thebag 100 e in a direction transverse (i.e., transverse direction) to adirection in which the film was extruded (i.e., machine direction). Inparticular, the thicker ribs 44 and the bonds 49 can extend from thebottom 94 of the bag 100 e to the top edge 102. As shown by FIG. 17, thebonded stripes or bonded regions 49 can extend across the entire lengthof the bag 100 e. One will appreciate in view of the disclosure hereinthat the striped pattern 36 may vary depending on the method used toincrementally stretch and partially discontinuously bond adjacent layersof film 10. To the extent that MD or other ring rolling is used tolightly bond the film 10, the striped pattern 36 (e.g., width andspacing of the stripes or stretched regions 44) on the film 10 candepend on the pitch 32 of the ridges 24, 26, the DOE 34, and otherfactors. As regions 49 represent areas of the multi-layer film in whichthe adjacent layers are lightly bonded to one another, it will beapparent that altering the spacing and/or width of regions 49 can affectthe overall strength of the film. For example, providing more bondedsurface area relative to the unbonded surface area can increase thedensity of such bonds that can absorb forces, increasing the filmstrength.

FIG. 18 illustrates a multi-layered bag 100 f similar to themulti-layered bag 100 e of FIG. 17, albeit that a lower section 124 b ofthe bag 100 f includes a strainable network in a pattern 36 c of diamondshaped ribs similar to that described herein in above in reference toFIGS. 9-11. Thus, the density of bonds in the middle section 124 b ofthe bag 100 f can be greater than the density of bonds in an uppersection 116 b of the multi-layer bag 100 f. Along related lines thelower section 124 b of the multi-layer bag 100 f can have a lowergauge-by-weight (i.e., be thinner on average) than the upper section 116b.

FIG. 18 further illustrates that the upper section 116 b can begin atthe hem seal and extend to the top edge 102 of the multi-layer bag 100f. Additionally, the lower section 124 b of the multi-layer bag 100 fcan extend from the hem seal to the bottom fold 64 of the multi-layerbag 100 f.

FIG. 19 illustrates yet another multi-layer bag 100 g similar to themulti-layer bag 100 e of FIG. 17. The multi-layer bag 100 g includes atop section 116 c that extends from the top edge 102 of the multi-layerbag 100 g to the hem seal 126. The multi-layer bag 100 g also includes abottom section 120 c that extends from the bottom 94 of the multi-layerbag 100 g toward the top edge 102. In one or more embodiments, the topsection 116 c and the bottom section 120 c can have approximately thesame width as shown in FIG. 19. The multi-layer bag 100 g can furtherinclude an upper section 116 d that extends from the top section 116 cand the hem seal 126 toward the bottom 94 of the multi-layer bag 100 g.In one or more embodiments, the upper section 116 d has a widthapproximately the same as or the same as the top and bottom sections 116c, 120 c. Finally, the multi-layer bag 100 g can include a middlesection 124 c located between the upper section 116 d and the bottomsection 120 c. The middle section 124 c can comprise the majority of themulti-layer bag 100 g as shown in FIG. 19.

As with the other multi-layer bags described herein, the multi-layer bag100 g can comprise an inner layer or film of material bonded to an outerlayer or film of material. FIG. 19 illustrates that the differentsections of the multi-layer bag 100 g can include different bondpatterns to provide the different areas of the multi-layer bag 100 gwith different properties. FIG. 19 illustrates that the entiremulti-layer bag 100 g can include a pattern 36 of thicker, bondedregions and stretched, unbounded regions as described above in relationto FIGS. 3A-4.

Furthermore, FIG. 19 illustrates that the bottom and top sections 120 c,116 c can consistent of the pattern 36 of thicker, bonded regions andstretched, unbounded regions (i.e., the only bonds in the bottom and topsections 120 c, 116 besides the side seals and hem seal(s) can be bondsformed by MD ring rolling). The upper section 116 c can further includea strainable network in a pattern 36 c of diamonds or anther shape asdescribed above in relation to FIGS. 9-11 in addition to the pattern 36of bonds. Finally, the middle section 124 c can include a pattern 36 aof MD extending thicker, bonded regions and stretched, unbounded regionsas described above in relation to FIGS. 5A-6.

FIG. 20 illustrates still another the multi-layer bag 100 h. Themulti-layer bag 100 h includes a top section 116 c that extends from thetop edge 102 of the multi-layer bag 100 g to the hem seal 126. Themulti-layer bag 100 h includes an upper section 116 d that extends fromthe top section 116 c and the hem seal 126 toward the bottom 94 of themulti-layer bag 100 g. In one or more embodiments, the top section 116 cand the upper section 116 d can have approximately or exactly the samewidth as shown in FIG. 20. Finally, the multi-layer bag 100 h caninclude a bottom section 125 that extends from the bottom 94 of themulti-layer bag 100 h toward to the upper section 116 d.

FIG. 20 illustrates that the multi-layered bag 100 h is similar to themulti-layered bag 100 e of FIG. 17, albeit that the upper section 116 dof the bag 100 f includes a strainable network in a pattern 36 c ofdiamond shaped ribs similar to that described herein in above inreference to FIGS. 9-11. Thus, the density of bonds in the upper section124 b of the bag 100 h can be greater than the density of bondselsewhere in the bag 115 c.

Thus, one will appreciate in view of the disclosure herein that amanufacturer can tailor specific sections or zones of a bag or film withdesirable properties by MD, TD, DD ring rolling, SELF'ing, orcombinations thereof. One will appreciate in view of the disclosureherein that one or more implementations can include bonded regionsarranged in other patterns/shapes. Such additional patterns include, butare not limited to, intermeshing circles, squares, diamonds, hexagons,or other polygons and shapes. Additionally, one or more implementationscan include bonded regions arranged in patterns that are combinations ofthe illustrated and described patterns/shapes.

In one or more implementations, each bonded pattern may have a largestTD patterned width in the transverse direction (TD) of less than about25% of the transverse width of the patterned film, or less than about20% of the transverse width of the film, or less than about 10% of thetransverse width of the patterned film, or less than about 5% of thetransverse width of the film. In one or more implementations, the bondedpatterns should have a largest MD patterned width in the machinedirection of less than about 25% of the machine width 140 of thepatterned film, or less than about 20% of the machine width of the film,or less than about 10% of the machine width of the film, or less thanabout 5% of the transverse width of the film.

In one or more implementations, the width of the bonded patterns in thetransverse direction may be greater than the width of the un-bondedareas in the transverse direction. The width of the bonded patterns inthe machine direction or direction perpendicular to the transversedirection may be greater than the width of the un-bonded areas in themachine direction.

The bond density of the multi-layered lightly-laminated films and bagsincorporating the same can be varied to control the bond strengthbetween the layers. For example, bonded areas of multi-layeredlightly-laminated films and bags incorporating the same can be large incomparison to un-bonded areas. For example, bonded areas ofmulti-layered lightly-laminated films and bags incorporating the samecan represent at least about 50% of the total area of the entire film,the entire bag, or the section where the lamination occurs, or at leastabout 60% of the entire film, the entire bag, or total area of thesection where the lamination occurs, at least about 70% of the entirefilm, the entire bag, or total area of the section where the laminationoccurs, at least about 80% of the total area of the entire film, theentire bag, or section where the lamination occurs. In otherembodiments, the bonded areas of multi-layered lightly-laminated filmsand bags incorporating the same can represent substantially less thanabout 50% of the total area of the entire film, the entire bag, orsection where the lamination occurs, or less than about 40% of the totalarea of the entire film, the entire bag, or section where the laminationoccurs, or less than about 30% of the total area of the entire film, theentire bag, or section where the lamination occurs, or less than about10% of the total area of the entire film, the entire bag, or sectionwhere the lamination occurs.

As mentioned previously, numerous methods can be used to provide thedesired degree of lamination in the bonded areas. Any of the describedring rolling techniques may be combined with other techniques in orderto further increase the strength of the lamination bond whilemaintaining bond strength below the strength of the weakest layer of themulti-layer film. For example, heat, pressure, ultrasonic bonding,corona treatment, or coating (e.g., printing) with adhesives may beemployed. Treatment with a corona discharge can enhance any of the abovemethods by increasing the tackiness of the film surface so as to providea stronger lamination bond, but which is still weaker than the tearresistance of the individual layers.

Adjusting (e.g., increasing) the strength of the relatively lightlamination bonding could be achieved by addition of a tackifier oradhesive to one or more of the skin plies of a multi-layer film, or byincorporating such a component into the material from which the filmlayer is formed. For example, the outer skin sublayers of a given layercould contain from about 0 to about 50% of a polyolefin plastomertackifier such as a C₄-C₁₀ olefin to adjust bonding strength byincreasing the tackiness of the surfaces of adjacent layers to belightly laminated.

In one or more implementations, a component may be included to decreasetackiness. For example, the outer skin sublayers could contain higherlevels of slip or anti-block agents, such as talc or oleamide (amide ofoleic acid), to decrease tack. Similarly, these surfaces may includevery low levels of or be substantially void of slip or anti-block agentsto provide a relative increase in tackiness. In still furtherembodiments the films 10 c, 10 c can be co-extruded together with a weakbond. Ring rolling or SELFing can then cause portions of the weak bondsto break thereby forming bonded and un-bonded regions such as thosedescribed hereinabove.

In another implementation, a pattern may be formed by embossing, in aprocess similar to ring rolling. Embossed patterns such as squares,diamonds, circles or other shapes may be embossed into a multi-layerfilm. The embossed, laminated film layers may be prepared by anysuitable means by utilizing two or more layers of preformed web of filmand passing them between embossing rollers. The method of embossingmultiple layers of film can involve calendar embossing two or moreseparate, non-laminated layers with discrete “icons” to form bondedareas or icons, each icon having a bonded length and separated fromadjacent icons by an equivalent un-bonded length. Such icons may be anydesired design or shape, such as a heart, square, triangle, diamond,trapezoid, or circle.

One or more implementations of the present invention can also includemethods of forming multi-layered lightly-laminated film with maintainedor decreased light transmittance and bags including the same. FIGS.21-24 and the accompanying description describe such methods. Of course,as a preliminary matter, one of ordinary skill in the art will recognizethat the methods explained in detail herein can be modified. Forexample, various acts of the method described can be omitted orexpanded, additional acts can be included, and the order of the variousacts of the method described can be altered as desired.

FIG. 21 illustrates an exemplary embodiment of a high-speedmanufacturing process 164 for creating multi-layered lightly-laminatedthermoplastic film(s) with maintained or decreased light transmittanceand then producing multi-layered plastic bags therefrom. According tothe process 164, a first thermoplastic film layer 10 c and a secondthermoplastic film layer 10 c′ are unwound from roll 165 a and 165 b,respectively, and directed along a machine direction. Alternatively, thefilm layers 10 c, 10 c′ can be directly from one or more extrusiontowers rather than stock rolls 165 a, 165 b. The first layer 10 c caninclude a first opacity agent and the second layer 10 c′ can include asecond opacity agent as described above.

The film layers 10 c, 10 c′ may pass between first and secondcylindrical intermeshing rollers 166, 167 to incrementally stretch andlightly laminate the initially separate film layers 10 c, 10 c′ tocreate un-bonded regions and bonded regions in at least one section of amulti-layered lightly-laminated film 15 a. The intermeshing rollers 166,167 shown in FIG. 21 have a construction similar to that of intermeshingrollers 12, 14 of FIGS. 3A-3B. In other embodiments, the intermeshingrollers 166, 167 can have the configuration of any of the otherintermeshing rollers shown or described herein. The rollers 166, 167 maybe arranged so that their longitudinal axes are perpendicular to themachine direction. Additionally, the rollers 166, 167 may rotate abouttheir longitudinal axes in opposite rotational directions as describedin conjunction with FIG. 3A. In various embodiments, motors may beprovided that power rotation of the rollers 166, 167 in a controlledmanner. As the film layers 10 c, 10 c′ pass between the first and secondrollers 166, 167 the ridges and/or teeth of the intermeshing rollers166, 167 can form a multi-layered lightly-laminated film 13.

During the manufacturing process 164, the multi-layeredlightly-laminated film 15 a can also pass through a pair of pinchrollers 169, 170. The pinch rollers 169, 170 can be appropriatelyarranged to grasp the multi-layered lightly-laminated film 15 a.

A folding operation 171 can fold the multi-layered lightly-laminatedfilm 15 a to produce the sidewalls of the finished bag. The foldingoperation 171 can fold the multi-layered lightly-laminated film 15 a inhalf along the transverse direction. In particular, the foldingoperation 171 can move a first edge 172 adjacent to the second edge 173,thereby creating a folded edge 174. The folding operation 171 therebyprovides a first film half 175 and an adjacent second web half 176. Theoverall width 177 of the second film half 176 can be half the width 177of the pre-folded multi-layered lightly-laminated film 15 a.

To produce the finished bag, the processing equipment may furtherprocess the folded multi-layered lightly-laminated film 15 a. Inparticular, a draw tape operation 178 can insert a draw tape 179 intoends 172, 173 of the multi-layered lightly-laminated film 15 a.Furthermore, a sealing operation 180 can form the parallel side edges ofthe finished bag by forming heat seals 181 between adjacent portions ofthe folded multi-layered lightly-laminated film 15 a. The heat seal 181may strongly bond adjacent layers together in the location of the heatseal 181 so as to tightly seal the edges of the finished bag. The heatseals 181 may be spaced apart along the folded multi-layeredlightly-laminated film 15 a to provide the desired width to the finishedbags. The sealing operation 180 can form the heat seals 181 using aheating device, such as, a heated knife.

A perforating operation 182 may form a perforation 183 in the heat seals181 using a perforating device, such as, a perforating knife. Theperforations 183 in conjunction with the folded outer edge 174 candefine individual bags 100 e that may be separated from themulti-layered lightly-laminated film 15 a. A roll 185 can wind themulti-layered lightly-laminated film 15 a embodying the finished bags184 for packaging and distribution. For example, the roll 185 may beplaced into a box or bag for sale to a customer.

In still further implementations, the folded multi-layeredlightly-laminated film 15 a may be cut into individual bags along theheat seals 181 by a cutting operation. In another implementation, thefolded multi-layered lightly-laminated film 15 a may be folded one ormore times prior to the cutting operation. In yet anotherimplementation, the side sealing operation 180 may be combined with thecutting and/or perforation operations 182.

One will appreciate in view of the disclosure herein that the process164 described in relation to FIG. 21 can be modified to omit or expandedacts, or vary the order of the various acts as desired. For example,FIG. 22 illustrates another manufacturing process 164 a for producing aplastic bag from an intermittingly bonded and stretched multi-layer filmwith maintained or decreased light transmittance. FIG. 22 illustratesanother manufacturing process 164 a for producing a plastic bag from amulti-layered lightly-laminated film. The process 164 a is similar toprocess 164 of FIG. 19, except that the film layers 10 c, 10 c′ arefolded in half to form c-, u-, or j-folded films prior to beginning theprocess. Methods of forming c-, u-, or j-folded films are described inInternational Patent Application No. PCT/US14/24431 filed Mar. 12, 2014and entitled STOCK ROLLS CONTAINING A FIRST FOLDED FILM WITHIN A SECONDFOLDED FILM AND METHODS OF MAKING THE SAME and U.S. Patent ApplicationPublication No. 2013/0115396. Each of the above-referenced patents andapplications is hereby incorporated by reference in its entirety.

As shown, according to the process 164 a the fold films 13 directedalong a machine direction (i.e., the direction in which both filmsforming the fold films 13 were extruded). The fold films 13 pass betweenfirst and second cylindrical intermeshing rollers 166, 167 toincrementally stretch and lightly laminate the initially separate filmlayers 10 c, 10 c′ to create un-bonded regions and bonded regions. Theintermeshing rollers 166, 167 have a construction similar to that ofintermeshing rollers 12, 14 of FIGS. 1A-1B. In other embodiments, theintermeshing rollers 166, 167 can have the configuration of any of theother intermeshing rollers shown or described herein. As the fold films13 pass between the first and second rollers 166, 167 the ridges and/orteeth of the intermeshing rollers 166, 167 can form a multi-layeredlightly-laminated film. In other words, four layers of film (i.e., twohalves of each film folded over) can pass through the intermeshingrollers 166, 167 at the same time. One will appreciate in view of thedisclosure herein that the fold of the folded films 13 can be positionedopposite the side in which the draw tape 179 is inserted.

In particular, the intermeshing rollers 166, 167 can incrementallystretch the fold films 13 in the machine direction to form stretched,thinner regions 46. In one or more embodiments both of the films 10 c,10 c′ forming the fold films 13 are predominately oriented in themachine direction. In such embodiments, the intermeshing rollers 167,168 can further orient the stretched, thinner regions 46 in the machinedirection such that the stretched, thinner regions 46 are more orientedin the machine direction that the thicker regions 44 that areun-stretched or less stretched compared to the stretched, thinnerregions 46.

As the fold films 13 comprise two layers of film folded in a c, j, or u,the intermeshing rollers 166, 167 can lightly laminated not only theouter film layer to the inner film layer, but can also lightly laminatethe two halves of the inner layer together as they are proximate eachother. In such embodiments, after passing through the intermeshingrollers 166, 167, either before or after passing through the nip rollers169, 170, the fold films 13 can pass over a spreader bar. Passing overthe spreader bar can separate the two halves of the fold films 13 andbreak any bonds between the two halves of the inner layer formed whenpassing through the intermeshing rollers 166, 167.

As described above in relation to FIG. 21, the process can furtherinvolve inserting a draw tape 179 into ends of nowincrementally-stretched and lightly laminated films 13. Furthermore, asealing operation 180 can form the parallel side edges of the finishedbag by forming heat seals 181 between adjacent portions of the foldedmulti-layered lightly-laminated film 10 b. The heat seal 181 maystrongly bond adjacent layers together in the location of the heat seal181 so as to tightly seal the edges of the finished bag. The heat seals181 may be spaced apart along the folded multi-layered lightly-laminatedfilm 10 b to provide the desired width to the finished bags. The sealingoperation 180 can form the heat seals 181 using a heating device, suchas, a heated knife.

A perforating operation 182 may form a perforation 183 in the heat seals181 using a perforating device, such as, a perforating knife. Theperforations 183 in conjunction with the folded outer edge 174 candefine individual bags 100 e (see e.g., FIG. 17) that may be separatedfrom the multi-layered lightly-laminated film assembly 13. A roll 185can wind the multi-layered lightly-laminated film 10 b embodying thefinished bags 184 for packaging and distribution. For example, the roll185 may be placed into a box or bag for sale to a customer.

In still further implementations, the folded multi-layeredlightly-laminated film 10 b may be cut into individual bags along theheat seals 181 by a cutting operation. In another implementation, thefolded multi-layered lightly-laminated film assembly 13 may be foldedone or more times prior to the cutting operation. In yet anotherimplementation, the side sealing operation 180 may be combined with thecutting and/or perforation operations 182.

FIG. 23 illustrates another manufacturing process 164 b for producing amulti-layered lightly-laminated film and a multi-layered bag (e.g., bag100 a of FIG. 17 or 100 h of FIG. 20) therefrom. The process 164 b canbe similar to process 164 a of FIG. 22, except that the fold filmassembly 13 can pass through a second set of intermeshing rollers 166 a,167 a, respectively, after passing through intermeshing rollers 166,167. In one or more embodiments, the intermeshing rollers 166 a, 167 acan comprise SELFing rollers (similar to those described above inrelation to FIG. 9). The intermeshing rollers 166 a, 167 a can furtherstretch and lightly bond at least a portion of the layers of the foldedfilm assembly 13 together. For example, as described above, theintermeshing rollers 166 a, 167 a can further stretch the film assemblyand form a strainable network in the film assembly. Passing the layersof the film assembly 13 simultaneously together through the pair ofSELFing rollers can comprises passing the layers of the film assemblysimultaneously together through a pair of SELFing rollers havingintermeshing teeth extending along only a portion of a length of eachroller so as to only create strainable networks in a portion (e.g.,portion 124 b of FIG. 16 or portion 116 d of FIGS. 19 and 20) of thefilm assembly 13.

FIG. 24 illustrates yet another manufacturing process 164 c forproducing a multi-layered lightly-laminated film and a multi-layered bag100 h therefrom. The process 164 c can be similar to process 164 b ofFIG. 23, except that the fold film assembly 13 can pass through a thirdset of intermeshing rollers 166 b, 167 b, respectively, after passingthrough intermeshing rollers 166, 167, 166 a, 167 a. In one or moreembodiments, the intermeshing rollers 166 b, 167 b can comprise TDrollers (similar to those described above in relation to FIGS. 5A-5B).The intermeshing rollers 166 b, 167 b can further stretch and lightlybond at least a portion of the layers of the folded film assembly 13together. For example, as described above, the intermeshing rollers 166b, 167 b can further stretch the film assembly and form a strainablenetwork in the film assembly. Passing the layers of the film assembly 13simultaneously together through the pair of SELFing rollers can formmachine-direction extending stretched regions, machine-directionextending thicker ribs, and machine-direction extending bonds thatsecure machine-direction thicker ribs in outer film-layer tomachine-direction thicker ribs in the inner film-layer.

Accordingly, FIGS. 1A-24 and the corresponding text, therefore,specifically show, describe, or otherwise provide a number of systems,components, apparatus, and methods for forming an intermittingly bondedand stretched multi-layer film with maintained or decreased lighttransmittance. These apparatus and methods can stretch films asdiscussed that, at the very least, avoid, increasing the film's lighttransmittance despite a reduction in gauge. There are several advantagesassociated with incrementally stretching and lightly bonding twothermoplastic films in accordance with one or more implementations ofthe present invention. First, incrementally stretching and lightlybonding two thermoplastic films can reduce the amount of thermoplasticmaterial needed to produce a film of certain dimensions. Manufacturerscan decrease the cost of their products if they use less thermoplasticmaterial in their products. Depending on the amount that a film isstretched, this cost savings can be significant.

Second, the ribbed pattern that is imparted onto anincrementally-stretched film can make the film feel more durable toconsumers. This can be important because consumers of products made inwhole or in part from a thermoplastic film often associate the strengthof a film with its feel. If a film feels thin or insubstantial,consumers may believe that the film is weak and fragile.

Third, incrementally stretching and lightly bonding two thermoplasticfilms in accordance with one or more implementations of the presentinvention, the films' light transmittance can be maintained or evendecreased. This finding is unexpected, as it is generally understoodthat stretching a thermoplastic film will increase the film's lighttransmittance. Indeed, in one or more implementations the lighttransmittance of a thermoplastic film can be maintained or decreaseddespite the reduction in gauge.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example, theillustrated and described implementations involve non-continuous (i.e.,discontinuous or partially discontinuous lamination) to provide the weakbonds. In alternative implementations, the lamination may be continuous.For example, multi film layers could be co-extruded so that the layershave a bond strength that provides for delamination prior to filmfailure to provide similar benefits to those described above. Thus, thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

I claim:
 1. A method of manufacturing a thermoplastic film with enhancedlight transmission, comprising: extruding a first layer of thermoplasticmaterial having a first concentration of a light-reflecting opacityagent, the first concentration of the light-reflecting opacity agentbeing between about 4% and about 6%; extruding a second layer ofthermoplastic material having a second concentration of alight-absorbing opacity agent, the second concentration of thelight-absorbing opacity agent in the second layer of thermoplasticmaterial being between 0.25% and 0.75% such that the second layer ofthermoplastic material has a cloudy transparent appearance;incrementally stretching the first and second layers by passing thefirst and second layers between one or more pairs of intermeshingrollers; and discontinuously bonding the first and second layerstogether.
 2. The method as recited in claim 1, wherein the first layerand the second layer each have an initial thickness of about 0.45 milswhen extruded.
 3. The method as recited in claim 1, further comprisingforming the thermoplastic film into a bag.
 4. The method as recited inclaim 1, wherein discontinuously bonding the first and second layerstogether comprises passing the first and second layers together througha first pair of intermeshing rollers.